1. Feely, R.A., R. Wanninkhof, P. Landschützer, B. Carter, and J.A. Trinanes. Global ocean carbon cycle. In State of the Climate in 2016, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 98(8):S89-S92, doi:10.1175/2017BAMSStateoftheClimate.1 2017

    Abstract:

    No abstract.

  2. Laurent, A., K. Fennel, W.-J. Cai, W.-J. Huang, L. Barbero, and R. Wanninkhof. Eutrophication-induced acidification of coastal waters in the northern Gulf of Mexico: Insights into origin and processes from a coupled physical-biogeochemical model. Geophysical Research Letters, 44(2):946-956, doi:10.1002/2016GL071881 2017

    Abstract:

    Nutrient inputs from the Mississippi/Atchafalaya River system into the northern Gulf of Mexico promote high phytoplankton production and lead to high respiration rates. Respiration coupled with water column stratification results in seasonal summer hypoxia in bottom waters on the shelf. In addition to consuming oxygen, respiration produces carbon dioxide (CO2), thus lowering the pH and acidifying bottom waters. Here we present a high-resolution biogeochemical model simulating this eutrophication-driven acidification and investigate the dominant underlying processes. The model shows the recurring development of an extended area of acidified bottom waters in summer on the northern Gulf of Mexico shelf that coincides with hypoxic waters. Not reported before, acidified waters are confined to a thin bottom boundary layer where the production of CO2 by benthic metabolic processes is dominant. Despite a reduced saturation state, acidified waters remain supersaturated with respect to aragonite.

  3. Lee, S.-K., D.L. Volkov, H. Lopez, W.G. Cheon, A.L. Gordon, Y. Liu, and R. Wanninkhof. Wind-driven ocean dynamics impact on the contrasting sea-ice trends around West Antarctica. Journal of Geophysical Research-Oceans, 122(5):4413-4430, doi:10.1002/2016JC012416 2017

    Abstract:

    Since late 1978, Antarctic sea-ice extent in the East Pacific has retreated persistently over the Amundsen and Bellingshausen Seas in warm seasons, but expanded over the Ross and Amundsen Seas in cold seasons, while almost opposite seasonal trends have occurred in the Atlantic over the Weddell Sea. By using a surface-forced ocean and sea-ice coupled model, we show that regional wind-driven ocean dynamics played a key role in driving these trends. In the East Pacific, the strengthening Southern Hemisphere (SH) westerlies in the region enhanced the Ekman upwelling of warm upper Circumpolar Deep Water and increased the northward Ekman transport of cold Antarctic surface water. The associated surface ocean warming south of 68°S and the cooling north of 68°S directly contributed to the retreat of sea-ice in warm seasons and the expansion in cold seasons, respectively. In the Atlantic, the poleward shifting SH westerlies in the region strengthened the northern branch of the Weddell Gyre which, in turn, increased the meridional thermal gradient across it as constrained by the thermal wind balance. Ocean heat budget analysis further suggests that the strengthened northern branch of the Weddell Gyre acted as a barrier against the poleward ocean heat transport, and thus produced anomalous heat divergence within the Weddell Gyre and anomalous heat convergence north of the gyre. The associated cooling within the Weddell Gyre and the warming north of the gyre contributed to the expansion of sea-ice in warm seasons and the retreat in cold seasons, respectively.

  4. Reimer, J.J., W.-J. Cai, L. Xue, R. Vargas, S. Noakes, X. Hu, S.R. Signorini, J.T. Mathis, R.A. Feely, A.J. Sutton, C. Sabine, S. Musielewicz, B. Chen, and R. Wanninkhof. Time series pCO2 at a coastal mooring: Internal consistency, seasonal cycles, and interannual variability. Continental Shelf Research, 145:95-108, doi:10.1016/j.csr.2017.06.022 2017

    Abstract:

    Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. Monitored parameters include all, or some, of the following: partial pressure of CO2 of the water (pCO2w) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray's Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of pCO2w from an underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual pCO2w time series variability and air-sea flux (FCO2), as well as describe the potential sources of pCO2w variability; and determine the source/sink for atmospheric pCO2. Over the ~8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated-pCO2w strongly correlate with r-values >0.90. pCO2w and FCO2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series pCO2w increases by 5.2±1.4 µatm y−1 with FCO2 increasing 51 to 70 mmol m−2 y−1. The net FCO2 sign can switch interannually with the magnitude varying greatly. Non-thermal pCO2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term pCO2w increase.

  5. Sharp, J.D., R.H. Byrne, X. Liu, R.A. Feely, E.E. Cuyler, R. Wanninkhof, and S.R. Alin. Spectrophotometric determination of carbonate ion concentrations: Elimination of instrument-dependent offsets and calculation of in situ saturation states. Environmental Science and Technology, 51(6):9127-9136, doi:10.1021/acs.est.7b02266 2017

    Abstract:

    This work describes an improved algorithm for spectrophotometric determinations of seawater carbonate ion concentrations ([CO32–]spec) derived from observations of ultraviolet absorbance spectra in lead-enriched seawater. Quality-control assessments of [CO32–]spec data obtained on two NOAA research cruises (2012 and 2016) revealed a substantial intercruise difference in average Δ[CO32–] (the difference between a sample’s [CO32–]spec value and the corresponding [CO32–] value calculated from paired measurements of pH and dissolved inorganic carbon). Follow-up investigation determined that this discordance was due to the use of two different spectrophotometers, even though both had been properly calibrated. Here we present an essential methodological refinement to correct [CO32–]spec absorbance data for small but significant instrumental differences. After applying the correction (which, notably, is not necessary for pH determinations from sulfonephthalein dye absorbances) to the shipboard absorbance data, we fit the combined-cruise data set to produce empirically updated parameters for use in processing future (and historical) [CO32–]spec absorbance measurements. With the new procedure, the average Δ[CO32–] offset between the two aforementioned cruises was reduced from 3.7 μmol kg–1 to 0.7 μmol kg–1, which is well within the standard deviation of the measurements (1.9 μmol kg–1). We also introduce an empirical model to calculate in situ carbonate ion concentrations from [CO32–]spec. We demonstrate that these in situ values can be used to determine calcium carbonate saturation states that are in good agreement with those determined by more laborious and expensive conventional methods.

  6. Sutton, A.J., R. Wanninkhof, C.L. Sabine, R.A. Feely, M.F. Cronin, and R.A. Weller. Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific. Geophysical Research Letters, 44(11):5627-5636, doi:10.1002/2017GLL073814 2017

    Abstract:

    Variability and change in the ocean sink of anthropogenic carbon dioxide (CO2) have implications for future climate and ocean acidification. Measurements of surface seawater CO2 partial pressure (pCO2) and wind speed from moored platforms are used to calculate high-resolution CO2 flux time series. Here we use the moored CO2 fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO2, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO2 uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO2 values driven by warm anomalies cause this region to be a net annual CO2 source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO2 sink to source.

  7. Talley, L.D., G.C. Johnson, S. Purkey, R.A. Feely, and R. Wanninkhof. Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) provides key climate-relevant deep ocean observations. CLIVAR Variations, 15(2):8-14, 2017

    Abstract:

    No abstract.

  8. Wanninkhof, R., and J. Trinanes. The impact of changing wind speeds on gas transfer and its effect on global air-sea CO2 fluxes. Global Biogeochemical Cycles, 31(6):961-974, doi:10.1002/2016GB005592 2017

    Abstract:

    An increase in global wind speeds over time is affecting the global uptake of CO2 by the ocean. We determine the impact of changing winds on gas transfer and CO2 uptake by using the recently updated, global high-resolution, cross-calibrated multiplatform wind product (CCMP-V2) and a fixed monthly pCO2 climatology. In particular, we assess global changes in the context of regional wind speed changes that are attributed to large-scale climate reorganizations. The impact of wind on global CO2 gas fluxes as determined by the bulk formula is dependent on several factors, including the functionality of the gas exchange-wind speed relationship and the regional and seasonal differences in the air-water partial pressure of CO2 gradient (ΔpCO2). The latter also controls the direction of the flux. Fluxes out of the ocean are influenced more by changes in the low-to-intermediate wind speed range, while ingassing is impacted more by changes in higher winds because of the regional correlations between wind and ΔpCO2. Gas exchange-wind speed parameterizations with a quadratic and third-order polynomial dependency on wind, each of which meets global constraints, are compared. The changes in air-sea CO2 fluxes resulting from wind speed trends are greatest in the equatorial Pacific and cause a 0.03–0.04 Pg C decade−1 increase in outgassing over the 27 year time span. This leads to a small overall decrease of 0.00 to 0.02 Pg C decade−1 in global net CO2 uptake, contrary to expectations that increasing winds increase net CO2 uptake.

  9. Williams, N.L., L.W. Juranek, R.A. Feely, K.S. Johnson, J.L. Sarmiento, L.D. Talley, A.G. Dickson, A.R. Gray, R. Wanninkhof, J.L. Russell, S.C. Riser, and Y. Takeshita. Calculating surface ocean pCO2 from biogeochemical Argo floats equipped with pH: An uncertainty analysis. Global Biogeochemical Cycles, 31(3):591-604, doi:10.1002/2016GB005541 2017

    Abstract:

    More than 74 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10-day intervals have been deployed throughout the Southern Ocean. Calculating the surface ocean partial pressure of carbon dioxide (pCO2sw) from float pH has uncertainty contributions from the pH sensor, the alkalinity estimate, and carbonate system equilibrium constants, resulting in a relative standard uncertainty in pCO2sw of 2.4% (or 10 µatm at pCO2sw of 400 µatm). The calculated pCO2sw from several floats spanning a range of oceanographic regimes are compared to existing climatologies. In some locations, such as the Subantarctic zone, the float data closely match the climatologies, but in the Polar Antarctic Zone significantly higher pCO2sw are calculated in the wintertime, implying a greater air-sea CO2 efflux estimate. Our results, based on four representative floats, suggest that despite their uncertainty relative to direct measurements the float data can be used to improve estimates for air-sea carbon flux, as well as to increase knowledge of spatial, seasonal, and interannual variability in this flux.

  10. Xu, Y-Y., W.-J. Cai, Y. Gao, R. Wanninkhof, J. Salisbury, B. Chen, J.J. Reimer, S. Gonski, and N. Hussain. Short-term variability of aragonite saturation state in the central Mid-Atlantic Bight. Journal of Geophysical Research-Oceans, 122(5):4274-4290, doi:10.1002/2017JC012901 2017

    Abstract:

    The uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has resulted in a decrease in seawater aragonite saturation state (Ωarag), which affects the health of carbonate-bearing organisms and the marine ecosystem. A substantial short-term variability of surface water Ωarag, with an increase of up to 0.32, was observed in the central Mid-Atlantic Bight off the Delaware and the Chesapeake Bays over a short period of 10 days in summer 2015. High-frequency underway measurements for temperature, salinity, percentage saturation of dissolved oxygen, oxygen to argon ratio, pH, fCO2, and measurements based on discrete samples for pH, dissolved inorganic carbon, and total alkalinity are used to investigate how physical and biogeochemical processes contribute to the changes of Ωarag. Quantitative analyses show that physical advection and mixing processes are the dominant forces for higher Ωarag in slope waters while biological carbon removal and CO2 degassing contribute to increased Ωarag in shelf waters.

  11. Akhand, A., A. Chanda, S. Manna, S. Das, S. Hazra, R. Roy, S.B. Choudhury, K.H. Rao, V.K. Dadhwal, K. Chakraborty, K.M.G. Mostofa, T. Tokoro, T. Kuwae, and R. Wanninkhof. A comparison of CO2 dynamics and air-water fluxes in a river-dominated estuary and a mangrove-dominated marine estuary. Geophysical Research Letters, 43(22):11,726-11,735, doi:10.1002/2016GL070716 2016

    Abstract:

    The fugacity of CO2 (fCO2 (water)) and air-water CO2 flux were compared between a river-dominated anthropogenically disturbed open estuary, the Hugli, and a comparatively pristine mangrove-dominated semiclosed marine estuary, the Matla, on the east coast of India. Annual mean salinity of the Hugli Estuary (≈7.1) was much less compared to the Matla Estuary (≈20.0). All the stations of the Hugli Estuary were highly supersaturated with CO2 (annual mean ~ 2200 µatm), whereas the Matla was marginally oversaturated (annual mean ~ 530 µatm). During the postmonsoon season, the outer station of the Matla Estuary was under saturated with respect to CO2 and acted as a sink. The annual mean CO2 emission from the Hugli Estuary (32.4 mol C m−2 yr−1) was 14 times higher than the Matla Estuary (2.3 mol C m−2 yr−1). CO2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river-dominated estuary.

  12. Bakker, D.C.E., B. Pfeil, C.S. Landa, N. Metzl, K.M. O'Brien, A. Olsen, K. Smith, C. Cosca, S. Harasawa, S.D. Jones, S.-I. Nakaoka, Y. Nojiri, U. Schuster, T. Steinhoff, C. Sweeney, T. Takahashi, B. Tilbrook, C. Wada, R. Wanninkhof, S.R. Alin, C.F. Balestrini, L. Barbero, N.R. Bates, A.A. Bianchi, F. Bonou, J. Boutin, Y. Bozec, E.F. Burger, W.-J. Cai, R.D. Castle, L. Chen, M. Chierici, K. Currie, W. Evans, C. Featherstone, R.A. Feely, A. Fransson, C. Goyet, N. Greenwood, L. Gregor, S. Hankin, N.J. Hardman-Mountford, J. Harlay, J. Hauck, M. Hoppema, M.P. Humphreys, C.W. Hunt, B. Huss, J.S.P. Ibánhez, T. Johannessen, R. Keeling, V. Kitidis, A. Körtzinger, A. Kozyr, E. Krasakopoulou, A. Kuwata, P. Landschützer, S.K. Lauvset, N. Lefèvre, C. Lo Monaco, A. Manke, J.T. Mathis, L. Merlivat, F.J. Millero, P.M.S. Monteiro, D.R. Munro, A. Murata, T. Newberger, A.M. Omar, T. Ono, K. Paterson, D. Pearce, D. Pierrot, L.L. Robbins, S. Saito, J. Salisbury, R. Schlitzer, B. Schneider, R. Schweitzer, R. Sieger, I. Skjelvan, K.F. Sullivan, S.C. Sutherland, A.J. Sutton, K. Tadokoro, M. Telszewski, M. Tuma, S.M.A.C. Van Heuven, D. Vandemark, B. Ward, A.J. Watson, and S. Xu. A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT). Earth System Science Data, 8:383-413, doi:10.5194/essd-8-383-2016 2016

    Abstract:

    The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) “living data” publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID.

  13. Feely, R.A., R. Wanninkhof, B.R. Carter, J.N. Cross, J.T. Mathis, C.L. Sabine, C.E. Cosca, and J.A. Trinanes. Global ocean carbon cycle. In State of the Climate in 2015, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 97(8):S89-S92, 2016

    Abstract:

    No abstract.

  14. Ho, D.T., and R. Wanninkhof. Air-sea gas exchange in the North Atlantic: 3He/SF6 experiment during GasEx-98. Tellus B, 68:30198, doi:10.3402/tellusb.v68.30198 2016

    Abstract:

    GasEx-98 was the first open-ocean process study where gas transfer velocity measurements were made with several robust techniques, including airside eddy covariance of CO2 and deliberate injection of 3He and SF6. While the CO2 eddy covariance results have been fully analyzed and publicized, leading to a boom in the use of this technique in the marine environment, the 3He/SF6 results have not received the same level of analysis. Here, based on new approaches that we have developed to analyse 3He/SF6 data in the subsequent years, we revisit the 3He/SF6 dual tracer results from GasEx-98 and show that they are consistent with the results from other parts of the coastal and open ocean, and that they are in agreement with current parameterizations between wind speed and gas exchange for slightly soluble gases over the ocean at intermediate wind speeds.

  15. Talley, L.D., R.A. Feely, B.M. Sloyan, R. Wanninkhof, M.O. Baringer, J.L. Bullister, C.A. Carlson, S.C. Doney, R.A. Fine, E. Firing, N. Gruber, D.A. Hansell, M. Ishii, G.C. Johnson, K. Katsumata, R.M. Key, M. Kramp, C. Langdon, A.M. Macdonald, J.T. Mathis, E.L. McDonagh, S. Mecking, F.J. Millero, C.W. Mordy, T. Nakano, C.L. Sabine, W.M. Smethie, J.H. Swift, T. Tanhua, A.M. Thurnherr, M.J. Warner, and J.-Z. Zhang. Changes in ocean heat, carbon content, and ventilation: A review of the first decade of GO-SHIP global repeat hydrography. Annual Review of Marine Science, 8:185-215, doi:10.1146/annurev-marine-052915-100829 2016

    Abstract:

    Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth’s climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcing and ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (∼20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean’s overturning circulation.

  16. Wanninkhof, R., K. Johnson, N. Williams, J. Sarmiento, S. Riser, E. Briggs, S. Bushinsky, B. Carter, A. Dickson, R. Feely, A. Gray, L. Juranek, R. Key, L. Talley, J. Russel, and A. Verdy. An evaluation of pH and NO3 sensor data from SOCCOM floats and their utilization to develop ocean inorganic carbon products. SOCCOM Carbon System Working Group, White Paper, 30 pp., 2016

    Abstract:

    No abstract.

  17. Williams, N.L., L.W. Juranek, K.S. Johnson, R.A. Feely, S.C. Riser, L.D. Talley, J.L. Russell, J.L. Sarmiento, and R. Wanninkhof. Empirical algorithms to estimate water column pH in the Southern Ocean. Geophysical Research Letters, 43(7):3415-3422, doi:10.1002/2016GL068539 2016

    Abstract:

    Empirical algorithms are developed using high-quality GO-SHIP hydrographic measurements of commonly measured parameters (temperature, salinity, pressure, nitrate, and oxygen) that estimate pH in the Pacific sector of the Southern Ocean. The coefficients of determination, R2, are 0.98 for pH from nitrate (pHN) and 0.97 for pH from oxygen (pHOx) with RMS errors of 0.010 and 0.008, respectively. These algorithms are applied to Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) biogeochemical profiling floats, which include novel sensors (pH, nitrate, oxygen, fluorescence, and backscatter). These algorithms are used to estimate pH on floats with no pH sensors and to validate and adjust pH sensor data from floats with pH sensors. The adjusted float data provide, for the first time, seasonal cycles in surface pH on weekly resolution that range from 0.05 to 0.08 on weekly resolution for the Pacific sector of the Southern Ocean.

  18. Woosley, R.J., F.J. Millero, and R. Wanninkhof. Rapid anthropogenic changes in CO2 and pH in the Atlantic Ocean: 2003-2014. Global Biogeochemical Cycles, 30(1):70-90, doi:10.1002/2015GB005248 2016

    Abstract:

    The extended multilinear regression method is used to determine the uptake and storage of anthropogenic carbon in the Atlantic Ocean based on repeat occupations of four cruises from 1989 to 2014 (A16, A20, A22, and A10), with an emphasis on the 2003-2014 period. The results show a significant increase in basin-wide anthropogenic carbon storage in the North Atlantic, which absorbed 4.4 ± 0.9 Pg C decade1 from 2003 to 2014 compared to 1.9 ± 0.4 Pg C decade1 for the 1989-2003 period. This decadal variability is attributed to changing ventilation patterns associated with the North Atlantic Oscillation and increasing release of anthropogenic carbon into the atmosphere. There are small changes in the uptake rate of CO2 in the South Atlantic for these time periods (3.7 ± 0.8 Pg C decade1 versus 3.2 ± 0.7 Pg C decade1). Several eddies are identified as containing ~20% more anthropogenic carbon than the surrounding waters in the South Atlantic, demonstrating the importance of eddies in transporting anthropogenic carbon. The uptake of carbon results in a decrease in pH of ~0.0021 ± 0.0007 year1 for surface waters during the last 10 years, in line with the atmospheric increase in CO2.

  19. Yasunaka, S., A. Murata, E. Watanabe, M. Chierici, A. Fransson, S. van Heuven, M. Hoppema, M. Ishii, T. Johannessen, N. Kosugi, S.K. Lauvset, J.T. Mathis, S. Nishino, A.M. Omar, A. Olsen, D. Sasano, T. Takahashi, and R. Wanninkhof. Mapping of the air-sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability. Polar Science, 10(3):323-334, doi:10.1016/j.polar.2016.03.006 2016

    Abstract:

    We produced 204 monthly maps of the air–sea CO2 flux in the Arctic north of 60°N, including the Arctic Ocean and its adjacent seas, from January 1997 to December 2013 by using a self-organizing map technique. The partial pressure of CO2 in surface water data were obtained by shipboard underway measurements or calculated from alkalinity and total inorganic carbon of surface water samples. Subsequently, we investigated the basin-wide distribution and seasonal to interannual variability of the CO2 fluxes. The 17-year annual mean CO2 flux shows that all areas of the Arctic Ocean and its adjacent seas were net CO2 sinks. The estimated annual CO2 uptake by the Arctic Ocean was 180 TgC yr–1. The CO2 influx was strongest in winter in the Greenland/Norwegian Seas (>15 mmol m–2 day–1) and the Barents Sea (>12 mmol m–2 day–1) because of strong winds, and strongest in summer in the Chukchi Sea (∼10 mmol m–2 day–1) because of the sea-ice retreat. In recent years, the CO2 uptake has increased in the Greenland/Norwegian Sea and decreased in the southern Barents Sea, owing to increased and decreased air–sea pCO2 differences, respectively.

  20. Ballantyne, A.P., R. Andres, R. Houghton, B.D. Stocker, R. Wanninkhof, W. Anderegg, L.A. Cooper, M. DeGrandpre, P.P. Tans, J.B. Miller, C. Alden, and J.W.C. White. Audit of the global carbon budget: Estimate errors and their impact on uptake uncertainty. Biogeosciences, 12(8):2565-2584, doi:10.5194/bg-12-2565-2015 2015

    Abstract:

    Over the last 5 decades monitoring systems have been developed to detect changes in the accumulation of carbon (C) in the atmosphere and ocean; however, our ability to detect changes in the behavior of the global C cycle is still hindered by measurement and estimate errors. Here we present a rigorous and flexible framework for assessing the temporal and spatial components of estimate errors and their impact on uncertainty in net C uptake by the biosphere. We present a novel approach for incorporating temporally correlated random error into the error structure of emission estimates. Based on this approach, we conclude that the 2σ uncertainties of the atmospheric growth rate have decreased from 1.2 Pg C yr−1 in the 1960s to 0.3 Pg C yr−1 in the 2000s due to an expansion of the atmospheric observation network. The 2σ uncertainties in fossil fuel emissions have increased from 0.3 Pg C yr−1 in the 1960s to almost 1.0 Pg C yr−1 during the 2000s due to differences in national reporting errors and differences in energy inventories. Lastly, while land use emissions have remained fairly constant, their errors still remain high and thus their global C uptake uncertainty is not trivial. Currently, the absolute errors in fossil fuel emissions rival the total emissions from land use, highlighting the extent to which fossil fuels dominate the global C budget. Because errors in the atmospheric growth rate have decreased faster than errors in total emissions have increased, a ~20% reduction in the overall uncertainty of net C global uptake has occurred. Given all the major sources of error in the global C budget that we could identify, we are 93% confident that terrestrial C uptake has increased and 97% confident that ocean C uptake has increased over the last 5 decades. Thus, it is clear that arguably one of the most vital ecosystem services currently provided by the biosphere is the continued removal of approximately half of atmospheric CO2 emissions from the atmosphere, although there are certain environmental costs associated with this service, such as the acidification of ocean waters.

  21. Brown, P.J., L. Jullion, P. Landschützer, D.C.E. Bakker, A.C. Naveira Garabato, M.P. Meredith, S. Torres-Valdes, A.J. Watson, M. Hoppema, B. Loose, E.M. Jones, M. Telszewski, S.D. Jones, and R. Wanninkhof. Carbon dynamics of the Weddell Gyre, Southern Ocean. Global Biogeochemical Cycles, 29(3):288-306, doi:10.1002/2014GB005006 2015

    Abstract:

    The accumulation of carbon within the Weddell Gyre and its exchanges across the gyre boundaries are investigated with three recent full-depth oceanographic sections enclosing this climatically-important region. The combination of carbon measurements with ocean circulation transport estimates from a box inverse analysis reveals that deepwater transports associated with Warm Deep Water (WDW) and Weddell Sea Deep Water dominate the gyre's carbon budget, while a dual-cell vertical overturning circulation leads to both upwelling and the delivery of large quantities of carbon to the deep ocean. Historical sea surface pCO2 observations, interpolated using a neural network technique, confirm the net summertime sink of 0.044-0.058 ± 0.010 Pg C yr–1 derived from the inversion. However, a wintertime outgassing signal similar in size results in a statistically insignificant annual air-to-sea CO2 flux of 0.002 ± 0.007 Pg C yr–1 (mean 1998-2011) to 0.012 ± 0.024 Pg C yr–1 (mean 2008-2010) to be diagnosed for the Weddell Gyre. A surface layer carbon balance, independently derived from in situ biogeochemical measurements, reveals that freshwater inputs and biological drawdown decrease surface ocean inorganic carbon levels more than they are increased by WDW entrainment, resulting in an estimated annual carbon sink of 0.033 ± 0.021 Pg C yr–1. Although relatively less efficient for carbon uptake than the global oceans, the summertime Weddell Gyre suppresses the winter outgassing signal, while its biological pump and deepwater formation act as key conduits for transporting natural and anthropogenic carbon to the deep ocean where they can reside for long time scales.

  22. Fanning, K.A., R.T. Masserini, J. Walsh, R. Wanninkhof, K. Sullivan, J.I. Virmani, and C.A. Heill. An ammonium enrichment event in the surface ocean: Wind forcing and potential ramifications. Marine Chemistry, 174:26-34, doi:10.1016/j.marchem.2015.03.018 2015

    Abstract:

    Ammonium is a nutrient frequently preferred by microorganisms that photosynthesizes at the base of the marine food web and removes atmospheric carbon dioxide via carbon fixation. Because their photosynthesis is concentrated in the ocean's thin euphotic zone, its nutrient concentrations are critical to oceanic carbon fixation. Identification of replacement processes for euphotic-zone ammonium thus becomes important. These processes were investigated in a two-experiment, Lagrangian field study that produced results consistent with an apparent inverse effect of wind forcing on upper-ocean ammonium concentrations. At low wind speeds (especially ≤ 4 ms− 1), continuous seawater sampling, supported by sulfur-hexafluoride (SF6) water-mass tracing and meteorological measurements, detected 1.1–4.4-km-wide boluses of surface seawater exhibiting ammonium enrichments that were 5 - to-10-fold above background. In the first experiment, ammonium maxima comprising the enrichment event disappeared at higher wind speeds. In the second experiment, which had consistently higher wind speeds, an ammonium event composed of such maxima was never found. The apparent correlation between elevated ammonium concentrations and low wind stress could therefore be viewed as potentially important for understanding ammonium cycling and carbon fixation in the ocean.

  23. Feely, R.A., R. Wanninkhof, B. Carter, J.T. Mathis, and C.L. Sabine. Global oceans: Ocean carbon. In State of the Climate in 2014, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 96(7):S87-S90, 2015

    Abstract:

    No abstract.

  24. Landschützer, P., N. Gruber, F.A. Haumann, C. Rödenbeck, D.C.E. Bakker, S. van Heuven, M. Hoppema, N. Metzl, C. Sweeney, T. Takahashi, B. Tilbrook, and R. Wanninkhof. The reinvigoration of the Southern Ocean carbon sink. Science, 349(6253):1221-1224, doi10.1126/science.aab2620 2015

    Abstract: Several studies have suggested that the carbon sink in the Southern Ocean—the ocean’s strongest region for the uptake of anthropogenic CO2—has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002 and, by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized.

  25. Le Quéré, C., R. Moriarty, R.M. Andrew, G.P. Peters, P. Ciais, P. Friedlingstein, S.D. Jones, S. Sitch, P. Tans, A. Arneth, T.A. Boden, L. Bopp, Y. Bozec, J.G. Canadell, L.P. Chini, F. Chevallier, C.E. Cosca, I. Harris, M. Hoppema, R.A. Houghton, J.I. House, A.K. Jain, T. Johannessen, E. Kato, R.F. Keeling, V. Kitidis, K. Klein Goldewijk, C. Koven, C.S. Landa, P. Landschützer, A. Lenton, I.D. Lima, G. Marland, J.T. Mathis, N. Metzl, Y. Nojiri, A. Olsen, T. Ono, S. Peng, W. Peters, B. Pfeil, B. Poulter, M.R. Raupach, P. Regnier, C. Rödenbeck, S. Saito, J.E. Salisbury, U. Schuster, J. Schwinger, R. Séférian, J. Segschneider, T. Steinhoff, B.D. Stocker, A.J. Sutton, T. Takahashi, B. Tilbrook, G.R. van der Werf, N. Viovy, Y.-P. Wang, R. Wanninkhof, A. Wiltshire, and N. Zeng. Global carbon budget 2014. Earth System Science Data, 7(1):45-85, doi:10.5194/essd-7-47-2015 2015

    Abstract:

    Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover-change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2, and land-cover-change (some including nitrogen–carbon interactions). We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2004–2013), EFF was 8.9 ± 0.4 GtC yr−1, ELUC 0.9 ± 0.5 GtC yr−1, GATM 4.3 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 2.9 ± 0.8 GtC yr−1. For year 2013 alone, EFF grew to 9.9 ± 0.5 GtC yr−1, 2.3% above 2012, continuing the growth trend in these emissions, ELUC was 0.9 ± 0.5 GtC yr−1, GATM was 5.4 ± 0.2 GtC yr−1, SOCEAN was 2.9 ± 0.5 GtC yr−1, and SLAND was 2.5 ± 0.9 GtC yr−1. GATM was high in 2013, reflecting a steady increase in EFF and smaller and opposite changes between SOCEAN and SLAND compared to the past decade (2004–2013). The global atmospheric CO2 concentration reached 395.31 ± 0.10 ppm averaged over 2013. We estimate that EFF will increase by 2.5% (1.3–3.5%) to 10.1 ± 0.6 GtC in 2014 (37.0 ± 2.2 GtCO2 yr−1), 65% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the global economy. From this projection of EFF and assumed constant ELUC for 2014, cumulative emissions of CO2 will reach about 545 ± 55 GtC (2000 ± 200 GtCO2) for 1870–2014, about 75% from EFF and 25% from ELUC. This paper documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this living data set (Le Quéré et al., 2013, 2014). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2014).

  26. Patsavas, M.C., R.H. Byrne, B. Yang, R.A. Easley, R. Wanninkhof, and X. Liu. Procedures for direct spectrophotometric determination of carbonate ion concentrations: Measurements in U.S. Gulf of Mexico and east coast waters. Marine Chemistry, 168:80-85, doi:10.1016/j.marchem.2014.10.015 2015

    Abstract:

    Refined procedures were developed for directly determining carbonate ion concentrations in seawater through measurement of the ultraviolent absorbances of lead carbonate and chloride complexes after addition of divalent lead (Pb(II)) to a seawater sample. Our model algorithm is based on carbonate ion concentrations calculated from measurements of pH and dissolved inorganic carbon (DIC) obtained on a NOAA ocean acidification cruise (GOMECC-2, the second Gulf of Mexico and East Coast Carbon cruise). These calculated carbonate concentrations, in conjunction with Pb(II) absorbance measurements for the same seawater samples, were used to refine previous algorithms based on different chemical-measurement techniques and a limited range of carbonate concentrations. The precision of the spectrophotometric carbonate measurements is affected by the concentration of Pb(II) in the titrated seawater samples. Doubling the concentration of the titrant improved precision relative to previously published procedures but required formulation of a correction for changes in carbonate ion concentration caused by the titrant addition. Minor changes in the new algorithm for the spectrophotometric method produced carbonate ion values in excellent agreement with values calculated from paired pH and DIC observations over a carbonate concentration range of 73–258 μmol kg–1. This new algorithm, tested on three subsequent research cruises in the Gulf of Mexico, showed a random scatter of residuals and an average offset between measured and calculated carbonate concentrations equal to –0.92 ± 5.33 μmol kg–1.

  27. Patsavas, M.C., R.H. Byrne, R. Wanninkhof, R.A. Feely, and W.-J. Cai. Internal consistency of marine carbonate system measurements and assessments of aragonite saturation state: Insights from two U.S. coastal cruises. Marine Chemistry, 176:9-20, doi:10.1016/j.marchem.2015.06.022 2015

    Abstract:

    This research assesses the thermodynamic consistency of recent marine CO2 system measurements in United States coastal waters. As one means of assessment, we compared aragonite saturation states calculated using various combinations of measured parameters. We also compared directly measured and calculated values of total alkalinity and CO2 fugacity. The primary data set consists of state-of-the-art measurements of the keystone parameters of the marine CO2 system: dissolved inorganic carbon (DIC), total alkalinity (TA), CO2 fugacity (fCO2), and pH. This study is the first thermodynamic CO2 system intercomparison based on measurements obtained using purified meta cresol purple as a pH indicator. The data are from 1890 water samples collected during NOAA’s West Coast Ocean Acidification Cruise of 2011 (WCOA2011) and NOAA’s Gulf of Mexico and East Coast Carbon Cruise of 2012 (GOMECC-2). Calculations of in situ aragonite saturation states (ΩA) near the saturation horizon exhibited differences on the order of ±10% between predictions based on the (DIC, TA) pair of measurements versus the (pH, DIC), (fCO2, DIC), or (fCO2, pH) pairs. Differences of this magnitude, which are largely attributable to the imprecision of ΩA calculated from the (DIC, TA) pair, are roughly equivalent to the magnitude of ΩA change projected to occur over the next several decades due to ocean acidification. These observations highlight the importance of including either pH or fCO2 in saturation state calculations. Calculations of TA from (pH, DIC) and (fCO2, DIC) showed that internal consistency could be achieved if minor subtractions of TA (≤ 4 μmol kg−1) were applied to samples of salinity <35. The extent of thermodynamic consistency is also exemplified by the small offset between TA calculated from (DIC, pH) and that calculated from (DIC, fCO2): ~3 μmol kg−1, which is similar to the accuracy of the TA measurements. Systematic trends can be detected in the offsets between measured and calculated parameters, but for this high quality data set the magnitude of methodological improvements required to achieve exact thermodynamic consistency is quite small.

  28. Rios, A.F., L. Resplandy, M.I. Garcia-Ibanez, N.M. Fajar, A. Velo, X.A. Padin, R. Wanninkhof, R. Steinfeldt, G. Roson, and F.F. Perez. Decadal acidification in the water masses of the Atlantic Ocean. Proceedings of the National Academy of Sciences USA, 112(32):9950-9955, doi:10.1073/pnas.1504613112 2015

    Abstract:

    Global ocean acidification is caused primarily by the ocean’s uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S–36°N) for the Atlantic Ocean over two decades (1993–2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (∆pH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of −0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between −0.0015 and −0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic.

  29. Rödenbeck, C., D.C.E. Bakker, N. Gruber, Y. Iida, A.R. Jacobson, S. Jones, P. Landschützer, N. Metzl, S. Nakaoka, A. Olsen, G.-H. Park, P. Peylin, K.B. Rodgers, T.P. Sasse, U. Schuster, J.D. Shutler, V. Valsala, R. Wanninkhof, and J. Zeng. Data-based estimates of the ocean carbon sink variability—First results of the surface ocean pCO2 mapping intercomparison (SOCOM). Biogeosciences, 12(23):7251-7278, doi:10.5194/bg-12-7251-2015 2015

    Abstract:

    Using measurements of the surface-ocean CO2 partial pressure (pCO2) and 14 different pCO2 mapping methods recently collated by the Surface Ocean pCO2 Mapping intercomparison (SOCOM) initiative, variations in regional and global sea-air CO2 fluxes are investigated. Though the available mapping methods use widely different approaches, we find relatively consistent estimates of regional pCO2 seasonality, in line with previous estimates. In terms of interannual variability (IAV), all mapping methods estimate the largest variations to occur in the eastern equatorial Pacific. Despite considerable spread in the detailed variations, mapping methods that fit the data more closely also tend to agree more closely with each other in regional averages. Encouragingly, this includes mapping methods belonging to complementary types, taking variability either directly from the pCO2 data or indirectly from driver data via regression. From a weighted ensemble average, we find an IAV amplitude of the global sea-air CO2 flux of 0.31 PgC yr−1 (standard deviation over 1992-2009), which is larger than simulated by biogeochemical process models. From a decadal perspective, the global ocean CO2 uptake is estimated to have gradually increased since about 2000, with little decadal change prior to that. The weighted mean net global ocean CO2 sink estimated by the SOCOM ensemble is −1.75 PgC yr−1 (1992–2009), consistent within uncertainties with estimates from ocean-interior carbon data or atmospheric oxygen trends.

  30. Salisbury, J., D. Vandemark, B. Jonsson, W. Balch, S. Chakraborty, S. Lohrenz, B. Chapron, B. Hales, A. Mannino, J.T. Mathis, M. Reul, S.R. Signorini, R. Wanninkhof, and K.K. Yates. How can present and future satellite missions support scientific studies that address ocean acidification? Oceanography, 28(2):108-121, doi:10.5670/ oceanog.2015.35 2015

    Abstract:

    Space-based observations offer unique capabilities for studying spatial and temporal dynamics of the upper ocean inorganic carbon cycle and, in turn, supporting research tied to ocean acidification (OA). Satellite sensors measuring sea surface temperature, color, salinity, wind, waves, currents, and sea level enable a fuller understanding of a range of physical, chemical, and biological phenomena that drive regional OA dynamics, as well as the potentially varied impacts of carbon cycle change on a broad range of ecosystems. Here, we update and expand on previous work that addresses the benefits of space-based assets for OA and carbonate system studies. Carbonate chemistry and the key processes controlling surface ocean OA variability are reviewed. Synthesis of present satellite data streams and their utility in this arena are discussed, as are opportunities on the horizon for using new satellite sensors with increased spectral, temporal, and/or spatial resolution. We outline applications that include the ability to track the biochemically dynamic nature of water masses to map coral reefs at higher resolution, discern functional phytoplankton groups and their relationships to acid perturbations, and track processes that contribute to acid variation near the land-ocean interface.

  31. Wanninkhof, R., L. Barbero, R. Byrne, W.-J. Cai, W.-J. Huang, J.-Z. Zhang, M. Baringer, and C. Langdon. Ocean acidification along the gulf coast and east coast of the USA. Continental Shelf Research, 98:54-71, doi:10.1016/j.csr.2015.02.008 2015

    Abstract:

    As part of an effort to monitor changes in inorganic carbon chemistry of the coastal ocean, near-synoptic cruises are being conducted in the northern Gulf of Mexico and along the east coast of the United States. Here we describe observations obtained on a cruise in the summer of 2012 and compare them with results from a cruise following a similar track in 2007. The focus is on describing spatial patterns of aragonite saturation state (ΩAr). This parameter is an indicator of ecosystem health, in particular, for calcifying organisms. The results show large-scale regional trends from different source waters at the northeastern and southwestern edges of the domain, along with the modulating effects of remineralization/respiration and riverine inputs. The broader patterns and changes over five years along the coast can be well described by the impacts of large-scale circulation, notably changes in source waters contributions. Changes in the well-buffered Loop Current and Gulf Stream with high ΩAr impact the waters in the southern part of the study area. The less buffered southward coastal currents with low ΩAr originating from the Labrador Sea and Gulf of St. Lawrence impact the ΩAr patterns in the northern regions. The expected 2% average decrease in ΩAr in the surface mixed layer due to increasing atmospheric CO2 levels over the 5-year period is largely overshadowed by local and regional variability from changes in hydrography and mixed layer dynamics.

  32. Yang, B., R.H. Byrne, and R. Wanninkhof. Subannual variability of total alkalinity distributions in the northeastern Gulf of Mexico. Journal of Geophysical Research-Oceans, 120(5):3805-3816, doi:10.1002/2015JC010780 2015

    Abstract:

    The subannual variability of total alkalinity (TA) distributions in the northeastern Gulf of Mexico was examined through the use of TA data from ship-based water sampling, historical records of riverine TA, and contemporaneous model output of surface currents and salinity. TA variability was restricted to the upper 150 m of the water column, where relationships between salinity and TA were controlled primarily by subannual variations in the extent of mixing between seawater and river water. A transition in TA distribution patterns between the river-dominated northern margin (near the Mississippi-Atchafalaya River System) and the ocean current-dominated eastern margin (West Florida Shelf) was observed. An index for riverine alkalinity input was formulated to provide insights about riverine alkalinity contributions in the upper water column. Spatial and temporal variations of total alkalinity in the northeastern Gulf of Mexico are primarily controlled by riverine TA inputs and ocean currents.

  33. Bakker, D.C.E., B. Pfeil, K. Smith, S. Hankin, A. Olsen, S.R. Alin, C. Cosca, S. Harasawa, A. Kozyr, Y. Nojiri, K.M. O’Brien, U. Schuster, M. Telszewski, B. Tilbrook, C. Wada, J. Akl, L. Barbero, N.R. Bates, J. Boutin, Y. Bozec, W.-J. Cai, R.D. Castle, F.P. Chavez, L. Chen, M. Chierici, K. Currie, H.J.W. de Baar, W. Evans, R.A. Feely, A. Fransson, Z. Gao, B. Hales, N.J. Hardman-Mountford, M. Hoppema, W.-J. Huang, C.W. Hunt, B. Huss, T. Ichikawa, T. Johannessen, E.M. Jones, S.D. Jones, S. Jutterstrom, V. Kitidis, A. Kortzinger, P. Llandschutzer, S.K. Lauvset, N. Lefevre, A.B. Manke, J.T. Mathis, L. Merlivat, N. Metzl, A. Murata, T. Newberger, A.M. Omar, T. Ono, G.-H. Park, K. Paterson, D. Pierrot, A.F. Rios, C.L. Sabine, S. Saito, J. Salisbury, V.V.S.S. Sarma, R. Schlitzer, R. Sieger, I. Skjelvan, T. Steinhoff, K.F. Sullivan, H. Sun, A.J. Sutton, T. Suzuki, C. Sweeney, T. Takahashi, J. Tjiputra, N. Tsurushima, S.M.A.C. van Heuven, D. Vandemark, P. Vlahos, D.W.R. Wallace, R. Wanninkhof, and A.J. Watson. An update to the surface CO2 atlas (SOCAT version 2). Earth System Science Data, 6(1):69-90, doi:10.5194/essd-6-69-2014 2014

    Abstract:

    The Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO2 values) and extended data coverage (from 1968–2007 to 1968–2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink, and its spatial, seasonal, year-to-year and longer term variation, as well as initialization or validation of ocean carbon models and coupled climate-carbon models.

  34. Cai, W.-J., N.R. Bates, L. Guo, L.G. Anderson, J.T. Mathis, R. Wanninkhof, D.A. Hansell, L. Chen, and I.P. Semiletov. Carbon fluxes across boundaries in the Pacific Arctic region in a changing environment. In The Pacific Arctic Region: Ecosystem Status and Trends in a Rapidly Changing Environment, J.M. Grebmeier and W. Maslowski (eds.). Springer, Netherlands, 199-222, doi:10.1007/978-94-017-8863-2_8 2014

    Abstract:

    While the inflow of dissolved inorganic carbon (DIC) from the Pacific Ocean is relatively well quantified, the intermittent input from the East Siberian Sea (ESS) is not. The export flux to the Atlantic Ocean has unknown uncertainty due to a paucity of DIC data from the Canadian Archipelago. Within the region, the Chukchi Sea is the dominant site for atmospheric carbon dioxide (CO2) uptake, while the Beaufort Sea and the Canadian Archipelago take-up much less CO2 with latter potentially a weak source of CO2 during certain times of the year. Additionally, the ESS shelf is a net source of CO2. Summertime CO2 uptake capacity in the deep Canada Basin has increased greatly recently as sea-ice retreat progresses rapidly. The region appears to export more DIC than it receives by a small amount, suggesting that it is probably weakly net heterotrophic. In addition to labile organic carbon (OC) produced in the productive marginal seas, some riverine and coastal erosion-derived OC likely is also recycled. As warming progresses, the Arctic Ocean may produce and export more DIC. Whether this change will turn the Arctic Ocean into a weaker CO2 sink or even a CO2 source for the atmosphere is uncertain and dependent on multiple factors that control the rate of surface water CO2 increase versus the rate of the atmospheric CO2 increase.

  35. Feely, R.A., L.D. Talley, J.L. Bullister, C.A. Carlson, S.C. Doney, R.A. Fine, E. Firing, N. Gruber, D.A. Hansell, G.C. Johnson, R.M. Key, C. Langdon, A. Macdonald, J.T. Mathis, S. Mecking, F.J. Millero, C.W. Mordy, C.L. Sabine, W.M. Smethie, J.H. Swift, A.M. Thurnherr, R. Wanninkhof, and M.J. Warner. The U.S. Repeat Hydrography CO2/Tracer Program (GO-SHIP): Accomplishments from the first decadal survey. A U.S. CLIVAR and OCB Report, 2014-5, U.S. CLIVAR Project Office, 47 pp., 2014

    Abstract:

    No abstract.

  36. Feely, R.A., R. Wanninkhof, C.L. Sabine, J.T. Mathis, T. Takahashi, and S. Khatiwala. Global oceans: Global ocean carbon cycle. In State of the Climate in 2013, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 95(7):S73-S78, 2014

    Abstract:

    No abstract.

  37. Ishii, M., R.A. Feely, K.B. Rodgers, G.-H. Park, R. Wanninkhof, D. Sasano, H. Sugimoto, C.E. Cosca, S. Nakaoka, M. Telszewski, Y. Nojiri, S.E. Mikaloff Fletcher, Y. Niwa, P.K. Patra, V. Valsala, H. Nakano, I. Lima, S.C. Doney, E.T. Buitenhuis, O. Aumont, J.P. Dunne, A. Lenton, and T. Takahashi. Air-sea CO2 flux in the Pacific Ocean for the period 1990-2009. Biogeosciences, 11(3):709-734, doi:10.5194/bg-11-709-2014 2014

    Abstract:

    Air-sea CO2 fluxes over the Pacific Ocean are known to be characterized by coherent large-scale structures that reflect not only ocean subduction and upwelling patterns, but also the combined effects of wind-driven gas exchange and biology. On the largest scales, a large net CO2 influx into the extratropics is associated with a robust seasonal cycle, and a large net CO2 efflux from the tropics is associated with substantial interannual variability. In this work, we have synthesized estimates of the net air–sea CO2 flux from a variety of products, drawing upon a variety of approaches in three sub-basins of the Pacific Ocean, i.e., the North Pacific extratropics (18-66°N), the tropical Pacific (18°S-18°N), and the South Pacific extratropics (44.5-18°S). These approaches include those based on the measurements of CO2 partial pressure in surface seawater (pCO2sw), inversions of ocean-interior CO2 data, forward ocean biogeochemistry models embedded in the ocean general circulation models (OBGCMs), a model with assimilation of pCO2sw data, and inversions of atmospheric CO2 measurements. Long-term means, interannual variations and mean seasonal variations of the regionally integrated fluxes were compared in each of the sub-basins over the last two decades, spanning the period from 1990 through 2009. A simple average of the long-term mean fluxes obtained with surface water pCO2 diagnostics and those obtained with ocean-interior CO2 inversions are −0.47 ± 0.13 Pg C yr−1 in the North Pacific extratropics, +0.44 ± 0.14 Pg C yr−1 in the tropical Pacific, and −0.37 ± 0.08 Pg C yr−1 in the South Pacific extratropics, where positive fluxes are into the atmosphere. This suggests that approximately half of the CO2 taken up over the North and South Pacific extratropics is released back to the atmosphere from the tropical Pacific. These estimates of the regional fluxes are also supported by the estimates from OBGCMs after adding the riverine CO2 flux, i.e., −0.49 ± 0.02 Pg C yr−1 in the North Pacific extratropics, +0.41 ± 0.05 Pg C yr−1 in the tropical Pacific, and −0.39 ± 0.11 Pg C yr−1 in the South Pacific extratropics. The estimates from the atmospheric CO2 inversions show large variations amongst different inversion systems, but their median fluxes are consistent with the estimates from climatological pCO2sw data and pCO2sw diagnostics. In the South Pacific extratropics, where CO2 variations in the surface and ocean interior are severely undersampled, the difference in the air–sea CO2 flux estimates between the diagnostic models and ocean-interior CO2 inversions is larger (0.18 Pg C yr−1). The range of estimates from forward OBGCMs is also large (−0.19 to −0.72 Pg C yr−1). Regarding interannual variability of air–sea CO2 fluxes, positive and negative anomalies are evident in the tropical Pacific during the cold and warm events of the El Niño-Southern Oscillation in the estimates from pCO2sw diagnostic models and from OBGCMs. They are consistent in phase with the Southern Oscillation Index, but the peak-to-peak amplitudes tend to be higher in OBGCMs (0.40 ± 0.09 Pg C yr−1) than in the diagnostic models (0.27 ± 0.07 Pg C yr−1).

  38. Johnson, G.C., K.E. McTaggart, and R. Wanninkhof. Antarctic bottom water temperature changes in the western South Atlantic from 1989 to 2014. Journal of Geophysical Research-Oceans, 119(12):8567-8577, doi:10.1002/2014JC010367 2014

    Abstract:

    Warming of abyssal waters in recent decades contributes to global heat uptake and sea level rise. Repeat oceanographic section data in the western South Atlantic taken mostly in 1989 (1995 across the Scotia Sea), 2005, and 2014 are used to quantify warming in abyssal waters that spread northward through the region from their Antarctic origins in the Weddell Sea. While much of the Scotia Sea warmed between 1995 and 2005, only the southernmost portion, on the north side of the Weddell Gyre, continued to warm between 2005 and 2014. The abyssal Argentine Basin also warmed between 1989 and 2005, but again only the southernmost portion continued to warm between 2005 and 2014, suggesting a slowdown in the inflow of the coldest, densest Antarctic Bottom Waters into the western South Atlantic between 1989 and 2014. In contrast, the abyssal waters of the Brazil Basin warmed both between 1989 and 2005 and between 2005 and 2014, at a rate of about 2 m C yr-1. This warming is also assessed in terms of the rates of change of heights above the bottom for deep isotherms in each deep basin studied. These results, together with findings from previous studies, suggest the deep warming signal observed in the Weddell Sea after the mid-1970s Weddell Polynya was followed by abyssal warming in the Argentine Basin from the late 1970s through about 2005, then warming in the deep Vema Channel from about 1992 through at least 2010, and warming in the Brazil Basin from 1989 to 2014.

  39. Le Quere, C., G.P. Peters, R.J. Andres, R.M. Andrew, T. Boden, P. Ciais, P. Friedlingstein, R.A. Houghton, G. Marland, R. Moriarty, S. Sitch, P. Tans, A. Arneth, A. Arvanitis, D.C.E. Bakker, L. Bopp, J.G. Canadell, L.P. Chini, S.C. Doney, A. Harper, I. Harris, J.I. House, A.K. Jain, S.D. Jones, E. Kato, R.F. Keeling, K. Klein Goldewijk, A. Kortzinger, C. Koven, N. Lefevre, F. Maignan, A. Omar, T. Ono, G.-H. Park, B. Pfeil, B. Poulter, M.R. Raupach, P. Regnier, C. Rodenbeck, S. Saito, J. Schwinger, J. Segschneider, B.D. Stocker, T. Takahashi, B. Tilbrook, S. van Heuven, N. Viovy, R. Wanninkhof, A. Wiltshire, and S. Zaehle. Global carbon budget 2013. Earth System Science Data, 6(1):235-263, doi:10.5194/essd-6-235-2014 2014

    Abstract:

    Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil-fuel combustion and cement production (EFF) are based on energy statistics, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated for the first time in this budget with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2 and land cover change (some including nitrogen–carbon interactions). All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2003-2012), EFF was 8.6 ± 0.4 GtC yr−1, ELUC 0.9 ± 0.5 GtC yr−1, GATM 4.3 ± 0.1 GtC yr−1, SOCEAN 2.5 ± 0.5 GtC yr−1, and SLAND 2.8 ± 0.8 GtC yr−1. For year 2012 alone, EFF grew to 9.7 ± 0.5 GtC yr−1, 2.2% above 2011, reflecting a continued growing trend in these emissions, GATM was 5.1 ± 0.2 GtC yr−1, SOCEAN was 2.9 ± 0.5 GtC yr−1, and assuming an ELUC of 1.0 ± 0.5 GtC yr−1 (based on the 2001–2010 average), SLAND was 2.7 ± 0.9 GtC yr−1. GATM was high in 2012 compared to the 2003–2012 average, almost entirely reflecting the high EFF. The global atmospheric CO2 concentration reached 392.52 ± 0.10 ppm averaged over 2012. We estimate that EFF will increase by 2.1% (1.1–3.1%) to 9.9 ± 0.5 GtC in 2013, 61% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the economy. With this projection, cumulative emissions of CO2 will reach about 535 ± 55 GtC for 1870–2013, about 70% from EFF (390 ± 20 GtC) and 30% from ELUC (145 ± 50 GtC). This paper also documents any changes in the methods and data sets used in this new carbon budget from previous budgets (Le Quéré et al., 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2013_V2.3).

  40. Rhein, M., S.R. Rintoul, S. Aoki, E. Campos, D. Chambers, R.A. Feely, S. Gulev, G.C. Johnson, S.A. Josey, A. Kostianoy, C. Mauritzen, D. Roemmich, L.D. Talley, F. Wang, I. Allison, M. Aoyama, M. Baringer, N.R. Bates, T. Boyer, R.H. Byrne, S. Cooley, S. Cunningham, T. Delcroix, C.M. Domingues, S. Doney, J. Dore, P.J. Durack, R. Fine, M. Gonzalez-Davila, S. Good, N. Gruber, M. Hemer, D. Hydes, M. Ishii, S. Jacobs, T. Kanzow, D. Karl, G. Kaser, A. Kazmin, R. Key, S. Khatiwala, J. Kleypas, R. Kwok, K. Lee, E. Leuliette, M. Menendez, C. Mordy, J. Olafsson, J. Orr, A. Orsi, G.-H. Park, I. Polyakov, S.G. Purkey, B. Qiu, G. Reverdin, A. Romanou, S. Schmidtko, R. Schmitt, K. Shimada, D. Smith, T.M. Smith, U. Stober, L. Stramma, T. Suga, N. Swart, T. Takahashi, T. Tanhua, K. von Schuckmann, H. von Storch, X. Wang, R. Wanninkhof, S. Wijffels, P. Woodworth, I. Yashayaev, and L. Yu. Observations: Ocean. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [T.F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, 255-315, 2014

    Abstract:

    No abstract.

  41. Robbins, L.L., R. Wanninkhof, L. Barbero, X. Hu, S. Mitra, S. Yvon-Lewis, W.-J. Cai, W.-J. Huang, and T. Ryerson. Air-sea exchange. In Report of the U.S. Gulf of Mexico Carbon Cycle Synthesis Workshop, March 27-28, 2013. Ocean Carbon and Biogeochemistry Program and North American Carbon Program, H.M. Benway and P.G. Coble (eds.). American Carbon Program, 17-23, 2014

    Abstract:

    No abstract.

  42. Rodgers, K.B., O. Aumont, S.E. Mikaloff Fletcher, Y. Plancherel, L. Bopp, C. de Boyer Montegut, D. Iudicone, R.F. Keeling, G. Madec, and R. Wanninkhof. Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring. Biogeosciences, 11(15):4077-4098, doi:10.5194/bg-11-4077-2014 2014

    Abstract:

    Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model, where the objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000-2006, with a relative reduction with wind stirring on the order of 0.9 Pg C yr−1 over the region south of 45° S. This impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other ocean biogeochemical tracers. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong reduction on the order of 25-30% in the concentrations of NO3 exported in Subantarctic Mode Water (SAMW) to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry through its impact over the Southern Ocean.

  43. Wanninkhof, R. Relationship between wind speed and gas exchange over the ocean revisited. Limnology and Oceanography Methods, 12:351-362, doi:10.4319/lom.2014.12.351 2014

    Abstract:

    The relationship between gas exchange and wind speed is used extensively for estimating bulk fluxes of atmospheric gases across the air-sea interface. Here, I provide an update on the frequently used method of Wanninkhof (1992). The update of the methodology reflects advances that have occurred over the past two decades in quantifying the input parameters. The general principle of obtaining a relationship constrained by the globally integrated bomb-14CO2 flux into the ocean remains unchanged. The improved relationship is created using revised global ocean 14C inventories and improved wind speed products. Empirical relationships of the Schmidt number, which are necessary to determine the fluxes, are extended to 40°C to facilitate their use in the models. The focus is on the gas exchange of carbon dioxide, but the suggested functionality can be extended to other gases at intermediate winds (≈4-15 m s–1). The updated relationship, expressed as k = 0.251 <U2> (Sc/660)–0.5 where k is the gas transfer velocity, is the average squared wind speed, and Sc is the Schmidt number, has a 20% uncertainty. The relationship is in close agreement with recent parameterizations based on results from gas exchange process studies over the ocean.

  44. Wanninkhof, R., D.C.E. Bakker, N. Bates, A. Olsen, T. Steinhoff, and A. Sutton. Incorporation of alternative sensors in the SOCAT database and adjustments to dataset quality control flags. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, 26 pp., doi:10.3334/CDIAC/ OTG.SOCAT_ADQCF 2014

    Abstract:

    With the advent of new sensors and platforms to measure surface water carbon dioxide (CO2) levels, the dataset quality control (QC) criteria are updated in the Surface Ocean CO2 Atlas (SOCAT) to accommodate surface water fugacity of CO2 (fCO2w) data from these sensors. The current dataset QC flags and their rationale are described. The new sensors and platforms are briefly presented. Some changes in the criteria for assigning dataset QC flags and a new data quality flag are introduced. The term “dataset QC flag” replaces “cruise QC flag” to reflect the alternate platforms that are included in SOCAT. All dataset QC flags will incorporate a specified accuracy of the data. For equilibrator based systems the criteria for equilibrator pressure measurements are relaxed as they are unnecessary stringent for the accuracy of fCO2 in surface seawater. The acceptable comparison with other in situ data, defined as a high quality cross-over, will meet specific criteria of maximum distance, differences in fCO2w and sea surface temperature (SST) between two data sets. The scientist submitting the dataset will enter a preliminary dataset flag. Platform type including alternative platforms, such as buoys and self-propelled surface vehicles, will be provided in the metadata and will be available as a selectable option in the Live Access Server (LAS) for SOCAT. These updates facilitate better separation of data of differing origin and quality, and enable incorporation of fCO2w data from alternative platforms and sensors in SOCAT. The revised criteria will be implemented during quality control for all new and updated data sets in version 3 onwards, but not to data sets already in versions 1 or 2. To view recommendations the reader should peruse section 6. The updated criteria for dataset QC flags are in Table 3.

  45. Feely, R.A., R. Wanninkhof, C.L. Sabine, J.T. Mathis, T. Takahashi, S. Khatiwala, and G.-H. Park. Global oceans: Global ocean carbon cycle. In State of the Climate in 2012, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 94(8):S72-S75, doi:10.1175/2013BAMSStateoftheClimate.1 2013

    Abstract:

    No abstract.

  46. Huang, K., N. Cassar, R. Wanninkhof, and M. Bender. An isotope dilution method for high-frequency measurements of dissolved inorganic carbon concentration in the surface ocean. Limnology and Oceanography-Methods, 11:572-583, doi:10.4319/lom.2013.11.572 2013

    Abstract:

    An autonomous system using isotope dilution as its core method has been developed to obtain high-frequency measurements of dissolved inorganic carbon (DIC) concentrations in the surface ocean. This system accurately mixes a seawater sample and a 13C-labeled sodium bicarbonate solution (spike). The mixed solution is then acidified and sent through a gas permeable membrane contactor. CO2 derived from DIC in the mixture is extracted by a CO2-free gas stream and is sent to a cavity ring-down spectrometer to analyze its 13C/12C ratio. [DIC] of the seawater can then be derived from the measured 13C/12C, the known mixing ratio and the [DI13C] of the spike. The method has been tested under a wide [DIC] range (1800-2300 µmol/kg) in the laboratory. It has also been deployed on a cruise that surveyed ocean waters to the south of Florida. At a sampling resolution of 4 min (15 samples per hour), the relative standard deviation of DIC determined from the laboratory tests and the field deployment is ±0.07% and ±0.09%, respectively. The accuracy of the method is better than 0.1% except where [DIC] varies faster than 5 µmol/kg per minute. Based on the laboratory and field evaluations, we conclude that this method can provide accurate underway [DIC] measurements at high resolution in most oceanic regions.

  47. Pfeil, B., A. Olsen, D.C.E. Bakker, S. Hankin, H. Koyuk, A. Kozyr, J. Malczyk, A. Manke, N. Metzl, C.L. Sabine, J. Akl, S.R. Alin, N. Bates, R.G.J. Bellerby, A. Borges, J. Boutin, P.J. Brown, W.-J. Cai, F.P. Chavez, A. Chen, C. Cosca, A.J. Fassbender, R.A. Feely, M. González-Dávila, C. Goyet, B. Hales, N. Hardman-Mountford, C. Heinze, M. Hood, M. Hoppema, C.W. Hunt, D. Hydes, M. Ishii, T. Johannessen, S.D. Jones, R.M. Key, A. Körtzinger, P. Landschützer, S.K. Lauvset, N. Lefèvre, A. Lenton, A. Lourantou, L. Merlivat, T. Midorikawa, L. Mintrop, C. Miyazaki, A. Murata, A. Nakadate, Y. Nakano, S. Nakaoka, Y. Nojiri, A.M. Omar, X.A. Padin, G.-H. Park, K. Paterson, F.F. Perez, D. Pierrot, A. Poisson, A.F. Ríos, J.M. Santana-Casiano, J. Salisbury, V.V.S.S. Sarma, R. Schlitzer, B. Schneider, U. Schuster, R. Sieger, I. Skjelvan, T. Steinhoff, T. Suzuki, T. Takahashi, K. Tedesco, M. Telszewski, H. Thomas, B. Tilbrook, J. Tjiputra, D. Vandemark, T. Veness, R. Wanninkhof, A.J. Watson, R. Weiss, C.S. Wong, and H. Yoshikawa-Inoue. A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT). Earth System Science Data, 5(1):125-143, doi:10.5194/essd-5-125-2013 2013

    Abstract:

    A well-documented, publicly available global data set of surface ocean carbon dioxide (CO2) parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT) project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2, which had been subject to quality control (QC). Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC), were retrieved from data originators, public websites, and other data centers. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly-defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968-2007). Three types of data products are available: individual cruise files, a merged complete data set, and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities.

  48. Schuster, U., G.A. McKinley, N. Bates, F. Chevallier, S.C. Doney, A.R. Fay, M. Gonzalez-Davila, N. Gruber, S. Jones, J. Krijnen, P. Landschutzer, N. Lefevre, M. Manizza, J. Mathis, N. Metzl, A. Olsen, A.F. Rios, C. Rodenbeck, J.M. Santana-Casiano, T. Takahashi, R. Wanninkhof, and A.J. Watson. An assessment of the Atlantic and Arctic sea-air CO2 fluxes, 1990-2009. Biogeosciences, 10(1):607-627, doi:10.5194/bg-10-607-2013 2013

    Abstract: The Atlantic and Arctic oceans are critical components of the global carbon cycle. Here we quantify the net sea-air CO2 flux, for the first time, across different methodologies for consistent time and space scales, for the Atlantic and Arctic basins. We present the long-term mean, seasonal cycle, interannual variability, and trends in sea-air CO2 flux for the period 1990 to 2009, and assign an uncertainty to each. We use regional cuts from global observations and modelling products, specifically a pCO2-based CO2 flux climatology, flux estimates from the inversion of oceanic and atmospheric data, and results from six ocean biogeochemical models. Additionally, we use basin-wide flux estimates from surface ocean pCO2 observations based on two distinct methodologies. Our best estimate of the contemporary sea-to-air flux of CO2 (sum of anthropogenic and natural components) by the Atlantic between 40°S and 79°N is -0.49 ± 0.11 Pg C yr-1 and by the Arctic is -0.12 ± 0.06 Pg C yr-1, leading to a combined sea-to-air flux of -0.61 ± 0.12 Pg C yr-1 for the two decades (negative reflects ocean uptake). We do find broad agreement amongst methodologies with respect to the seasonal cycle in the subtropics of both hemispheres, but not elsewhere. Agreement with respect to detailed signals of interannual variability is poor; and correlations to the North Atlantic Oscillation are weaker in the North Atlantic and Arctic than in the equatorial region and South Subtropics. Linear trends for 1995 to 2009 indicate increased uptake and generally correspond between methodologies in the North Atlantic, but there is disagreement amongst methodologies in the equatorial region and south subtropics.

  49. Wang, Z.A., R. Wanninkhof, W.-J. Cai, R.H. Byrne, X. Hu, T.-H. Peng, and W.-J. Huang. The marine inorganic carbon system along the Gulf of Mexico and Atlantic coasts: Insights from a transregional coastal carbon study. Limnology and Oceanography, 58(1):325-342, doi:10.4319/lo.2013.58.1.0325 2013

    Abstract:

    Distributions of total alkalinity (TA), dissolved inorganic carbon (DIC), and other parameters relevant to the marine inorganic carbon system were investigated in shelf and adjacent ocean waters during a U.S. Gulf of Mexico and East Coast Carbon cruise in July-August 2007. TA exhibited near-conservative behavior with respect to salinity. Shelf concentrations were generally high in southern waters (Gulf of Mexico and east Florida) and decreased northward from Georgia to the Gulf of Maine. DIC was less variable geographically and exhibited strongly nonconservative behavior. As a result, the ratio of TA to DIC generally decreased northward. The spatial patterns of other CO2 system parameters closely followed those of the TA:DIC ratio. All sampled shelf waters were supersaturated with respect to aragonite (saturation state ΩA > 1). The most intensely buffered and supersaturated waters (ΩA > 5.0) were in northern Gulf of Mexico river-plume waters; the least intensely buffered and least supersaturated waters (ΩA < 1.3) were in the deep Gulf of Maine. Due to their relatively low pH, ΩA, and buffer intensity, waters of the northeastern U.S. shelves may be more susceptible to acidification pressures than are their southern counterparts. In the Mid-Atlantic Bight, alongshore mixing tended to increase DIC concentrations southward, but this effect was largely offset by the opposing effects of biogeochemical processing. In the Gulf of Mexico, downstream increases in Loop Current DIC suggested significant contributions from shelf and gulf waters, estimated at 9.1 x 109 mol C d-1. Off the southeastern U.S., along-flow chemical changes in the Florida Current were dominated by mixing associated with North Atlantic subtropical recirculation.

  50. Wanninkhof, R., G.-H. Park, T. Takahashi, C. Sweeney, R.A. Feely, Y. Nojiri, N. Gruber, S.C. Doney, G.A. McKinley, A. Lenton, C. Le Quere, C. Heinze, J. Schwinger, H. Graven, and S. Khatiwala. Global ocean carbon uptake: Magnitude, variability and trends. Biogeosciences, 10(3):1983-2000, doi:10.5194/bg-10-1983-2013 2013

    Abstract: The globally integrated sea-air anthropogenic carbon dioxide (CO2) flux from 1990 to 2009 is determined from models and data-based approaches as part of the Regional Carbon Cycle Assessment and Processes (RECCAP) project. Numerical methods include ocean inverse models, atmospheric inverse models, and ocean general circulation models with parameterized biogeochemistry (OBGCMs). The median value of different approaches shows good agreement in average uptake. The best estimate of anthropogenic CO2 uptake for the time period based on a compilation of approaches is 2.0 Pg C yr-1. The interannual variability in the sea-air flux is largely driven by large-scale climate reorganizations and is estimated at 0.2 Pg C yr-1 for the two decades with some systematic differences between approaches. The largest differences between approaches are seen in the decadal trends. The trends range from -0.13 (Pg C yr-1) decade-1 to 0.50 (Pg C yr-1) decade-1 for the two decades under investigation. The OBGCMs and the databased sea-air CO2 flux estimates show appreciably smaller decadal trends than estimates based on changes in carbon inventory, suggesting that methods capable of resolving shorter timescales are showing a slowing of the rate of ocean CO2 uptake. RECCAP model outputs for five decades show similar differences in trends between approaches.

  51. Wanninkhof, R., G.-H. Park, T. Takahashi, R.A. Feely, J.L. Bullister, and S.C. Doney. Changes in deep-water CO2 concentrations over the last several decades determined from discrete pCO2 measurements. Deep-Sea Research, Part I, 74:48-63, doi:10.1016/j.dsr.2012.12.005 2013

    Abstract: Detection and attribution of hydrographic and biogeochemical changes in the deep ocean are challenging due to the small magnitude of their signals and to limitations in the accuracy of available data. However, there are indications that anthropogenic and climate change signals are starting to manifest at depth. The deep ocean below 2000 m comprises about 50% of the total ocean volume, and changes in the deep ocean should be followed over time to accurately assess the partitioning of anthropogenic carbon dioxide (CO2) between the ocean, terrestrial biosphere, and atmosphere. Here we determine the changes in the interior deep-water inorganic carbon content by a novel means that uses the partial pressure of CO2 measured at 20°C, pCO2(20), along three meridional transects in the Atlantic and Pacific oceans. These changes are measured on decadal time scales using observations from the World Ocean Circulation Experiment (WOCE)/World Hydrographic Program (WHP) of the 1980s and 1990s and the CLIVAR/CO2 Repeat Hydrography Program of the past decade. The pCO2(20) values show a consistent increase in deep water over the time period. Changes in total dissolved inorganic carbon (DIC) content in the deep interior are not significant or consistent, as most of the signal is below the level of analytical uncertainty. Using an approximate relationship between pCO2(20) and DIC change, we infer DIC changes that are at the margin of detectability. However, when integrated on the basin scale, the increases range from 8-40% of the total specific water column changes over the past several decades. Patterns in chlorofluorocarbons (CFCs), along with output from an ocean model, suggest that the changes in pCO2(20) and DIC are of anthropogenic origin.

  52. Feely, R.A., C.L. Sabine, R.H. Byrne, F.J. Millero, A.G. Dickson, R. Wanninkhof, A. Murata, L.A. Miller, and D. Greeley. Decadal changes in the aragonite and calcite saturation state of the Pacific Ocean. Global Biogeochemical Cycles, 26:GB3001, 15 pp., doi:10.1029/2011GB004157 2012

    Abstract:

    Based on measurements from the WOCE/JGOFS global CO2 survey, the CLIVAR/CO2 Repeat Hydrography Program and the Canadian Line P survey, we have observed an average decrease of 0.34% yr-1 in the saturation state of surface seawater in the Pacific Ocean with respect to aragonite and calcite. The upward migrations of the aragonite and calcite saturation horizons, averaging about 1 to 2 m yr-1, are the direct result of the uptake of anthropogenic CO2 by the oceans and regional changes in circulation and biogeochemical processes. The shoaling of the saturation horizon is regionally variable, with more rapid shoaling in the South Pacific where there is a larger uptake of anthropogenic CO2. In some locations, particularly in the North Pacific Subtropical Gyre and in the California Current, the decadal changes in circulation can be the dominant factor in controlling the migration of the saturation horizon. If CO2 emissions continue as projected over the rest of this century, the resulting changes in the marine carbonate system would mean that many coral reef systems in the Pacific would no longer be able to sustain a sufficiently high rate of calcification to maintain the viability of these ecosystems as a whole, and these changes perhaps could seriously impact the thousands of marine species that depend on them for survival.

  53. Garzoli, S., G. Johnson, R. Wanninkhof, and B. Sloyan. Observations for climate: Expanding to the deep ocean. Proceedings, U.S. Integrated Ocean Observing System (IOOS) Summit, Interagency Ocean Observation Committee (IOOC), Herndon, VA, November 13-16, 2012. Community White Paper, 8 pp., 2012

    Abstract:

    The deep ocean plays a crucial role in aspects of the climate system on longer time-scales including the global heat budget, sea level rise, potential variations in the meridional overturning circulation, and long-term storage of climatically-relevant compounds such as CO2, among others. Expanding the ocean observing system towards being truly global will include adequately measuring the half of the ocean volume below 2000 m depth. This will require an increased commitment to the design and implementation of technologies for collecting deep ocean data and transmitting these data to shore in a cost-effective manner. This paper (based on the CWP of the same title) focuses on four of the fundamental areas where improvements to the observing system in the deep ocean are critical to the advancement of our understanding of climate science. These include deep circulation with an emphasis on "strong flows," ocean heat content, fresh water/salinity content, and CO2 content. It is clear that to continue working towards understanding of climate variations and their impact on society, it is imperative to maintain existing observing systems while improving and expanding the deep ocean components of the Global Ocean Observing System. Recommendations are provided for expanding the observing systems for deep circulation, for deep temperature and salinity variations (hence heat and fresh water estimates), and for deep observations of CO2 and other chemical tracers. Recommendations are also provided in areas where technological advances are required to improve the ability to collect this data remotely using either free-floating or fixed observing platforms.

  54. Park, G.-H., and R. Wanninkhof. A large increase of the CO2 sink in the western tropical North Atlantic from 2002-2009. Journal of Geophysical Research, 117:C08029, 10 pp., doi:10.1029/2011JC007803 2012

    Abstract:

    Determining a robust trend of surface ocean carbon dioxide (CO2) for a period shorter than a decade is challenging due to large seasonal variability and a sparsity of data. Here, we estimate the multiannual trend of surface CO2 in the region of 19°N-20°N, 65°W-68°W for the period of 2002-2009. We used an unprecedented number of high-quality underway data of the fugacity of CO2 in surface seawater (fCO2SW) collected from 137 cruises using an automated system onboard the cruise ship Explorer of the Seas. The growth rate of fCO2SW was estimated by two de-seasonalization approaches that showed similar and significantly lower values than the atmospheric increases, leading to a large increase in the CO2 sink. The seasonal difference in the trends was significant, with fCO2SW values in winter showing no increase, while summer fCO2SW values lagged only slightly with the atmosphere. We attribute the lack of an increase in winter fCO2SW values to sea surface temperature changes, which are closely correlated with the El Niño-Southern Oscillation cycle, and to changes in the mixed layer depth. The slower increase of fCO2SW is also related to decreases in salinity. The 8-year averaged annual net sea-air CO2 flux was -0.06 ± 0.18 mol m-2 yr-1 compared to a climatology that shows a flux out of the ocean of +0.11 mol m-2 yr-1. The increasing flux differs from previous, mostly longer-term results for regional studies and time series stations in the North Atlantic, which suggests a decrease or no change in oceanic CO2 uptake.

  55. Sabine, C.L., R.A. Feely, R. Wanninkhof, T. Takahashi, S. Khatiwala, and G.-H. Park. Global oceans: Global ocean carbon cycle. In State of the Climate in 2011, J. Blunden and D.S. Arndt (eds.). Bulletin of the American Meteorological Society, 93(7):S84-S89, doi:10.1175/2012BAMSStateoftheClimate.1 2012

    Abstract:

    No abstract.

  56. Wanninkhof, R., R. Feely, A. Sutton, C. Sabine, K. Tedesco, N. Gruber, and S. Doney. An integrated ocean carbon observing system (IOCOS). Proceedings, U.S. Integrated Ocean Observing System (IOOS) Summit, Interagency Ocean Observation Committee (IOOC), Herndon, VA, November 13-16, 2012. Community White Paper, 7 pp., 2012

    Abstract:

    The global ocean is undergoing fundamental and rapid changes in response to warming, changes in wind stress, atmospheric CO2 increases, and changes in the hydrologic cycle. Each of these factors has impacts on the ocean carbon cycle and the ability of the ocean to sequester CO2 from the atmospheric. In turn, changes in the ocean carbon cycle, and ocean warming and stratification, lead to changes in ocean biogeochemistry and ecology. Feedbacks and impacts are complex and not fully understood. However, rapid advances in observing system technology are occurring, along with improvements in models and understanding of the system. A comprehensive integrated ocean carbon observing system (IOCOS) to understand and monitor these changes is within reach in the next decade. Rather than relying on a single approach or parameter, the IOCOS will be composed of an integrated system of ongoing surface and subsurface observations, modeling, and assessments. This observing element will also rely heavily on other parts of the International Ocean Observing System (IOOS). It will include new technology and modeling approaches to quantify carbon fluxes and inventories in the world’s oceans.

  57. Barbero, L., J. Boutin, L. Merlivat, N. Martin, T. Takahashi, S.C. Sutherland, and R. Wanninkhof. Importance of water mass formation regions for the air-sea CO2 flux estimate in the Southern Ocean. Global Biogeochemical Cycles, 25:GB1005, 16 pp., doi:10.1029/2010GB003818 2011

    Abstract:

    CARIOCA drifters and ship data from several cruises in the Subantarctic Zone (SAZ) of the Pacific Ocean, approximately 40°S-55°S, have been used in order to investigate surface CO2 partial pressure (pCO2) and dissolved inorganic carbon (DIC) patterns. The highest DIC values were determined in regions of deep water formation, characterized by deep mixed layer depths (MLD) as estimated from Argo float profiles. As a result, these areas act as sources of CO2 to the atmosphere. Using an empirical linear relationship between DIC, sea surface temperature (SST), and MLD, we then combine DIC with AT based on salinity and compute pCO2. Finally, we derive monthly fields of air-sea CO2 flux in the SAZ. Our fit predicts the existence of a realistic seasonal cycle, close to equilibrium with the atmosphere in winter and a sink when biological activity takes place. It also reproduces the impact that deep water formation regions close to the Subantarctic Front (SAF) and in the eastern part of the SAZ have on the uptake capacity of the area. These areas, undersampled in previous studies, have high pCO2, and as a result, our estimates (0.05 - 0.03 PgC yr-1) indicate that the Pacific SAZ acts as a weaker sink of CO2 than suggested by previous studies which neglect these source regions.

  58. Bender, M.L., S. Kinter, N. Cassar, and R. Wanninkhof. Evaluating gas transfer velocity parameterizations using upper ocean radon distributions. Journal of Geophysical Research, 116:C02010, 11 pp., doi:10.1029/2009JC005805 2011

    Abstract:

    Sea-air fluxes of gases are commonly calculated from the product of the gas transfer velocity (k) and the departure of the seawater concentration from atmospheric equilibrium. Gas transfer velocities, generally parameterized in terms of wind speed, continue to have considerable uncertainties, partly because of limited field data. Here we evaluate commonly used gas transfer parameterizations using a historical data set of 222Rn measurements at 105 stations occupied on Eltanin cruises and the Geosecs program. We make this evaluation with wind speed estimates from meteorological reanalysis products (from National Centers for Environmental Prediction and European Centre for Medium-Range Weather Forecasting) that were not available when the 222Rn data were originally published. We calculate gas transfer velocities from the parameterizations by taking into account winds in the period prior to the date that 222Rn profiles were sampled. Invoking prior wind speed histories leads to much better agreement than simply calculating parameterized gas transfer velocities from wind speeds on the day of sample collection. For individual samples from the Atlantic Ocean, where reanalyzed winds agree best with observations, three similar recent parameterizations give k values for individual stations with an rms difference of ~40% from values calculated using 222Rn data. Agreement of basin averages is much better. For the global data set, the average difference between k constrained by 222Rn and calculated from the various parameterizations ranges from -0.2 to +0.9 m/d (average, 2.9 m/d). Averaging over large domains, and working with gas data collected in recent years when reanalyzed winds are more accurate, will further decrease the uncertainties in sea-air fluxes.

  59. Goodkin, N.F., N.M. Levine, S.C. Doney, and R. Wanninkhof. Impacts of temporal CO2 and climate trends on the detection of ocean anthropogenic CO2 accumulation. Global Biogeochemical Cycles, 25:GB3023, 11 pp., doi:10.1029/2010GB004009 2011

    Abstract: A common approach for estimating the oceanic uptake of anthropogenic carbon dioxide (Canthro) depends on the linear approximation of oceanic dissolved inorganic carbon (DIC) from a suite of physical and biological ocean parameters. The extended multiple linear regression (eMLR) method assumes that baseline correlations and the resulting residual fields will remain constant with time even under the influence of secular climate changes. The validity of these assumptions over the 21st century is tested using a coupled carbon-climate model. Findings demonstrate that the influence of both changing climate and changing chemistry beyond 2-4 decades invalidates the assumption that the residual fields will remain constant resulting in significant errors in the eMLR estimate of Canthro. This study determines that the eMLR method is unable to describe Canthro uptake for a sampling interval of greater than 30 years if the error is to remain below 20% for many regions in the Southern Ocean, Atlantic Ocean, and western Pacific Ocean. These results suggest that, for many regions of the ocean basins, hydrographic field investigations have to be repeated at approximately decadal timescales in order to accurately predict the uptake of Canthro by the ocean if the eMLR method is used.

  60. Ho, D.T., C.L. Sabine, D. Hebert, D.S. Ullmann, R. Wanninkhof, R.C. Hamme, P.G. Strutton, B. Hales, J.B. Edson, and B.R. Hargreaves. Southern Ocean Gas Exchange Experiment: Setting the stage. Journal of Geophysical Research, 116:C00F08, 19 pp., doi:10.1029/2010JC006852 2011

    Abstract:

    The Southern Ocean Gas Exchange Experiment (SO GasEx) is the third in a series of U.S.-led open ocean process studies aimed at improving the quantification of gas transfer velocities and air-sea CO2 fluxes. Two deliberate 3He/SF6 tracer releases into relatively stable water masses selected for large ΔpCO2 took place in the southwest Atlantic sector of the Southern Ocean in austral fall of 2008. The tracer patches were sampled in a Lagrangian manner, using observations from discrete CTD/Rosette casts, continuous surface ocean and atmospheric monitoring, and autonomous drifting instruments to study the evolution of chemical and biological properties over the course of the experiment. CO2 and DMS fluxes were directly measured in the marine air boundary layer with micrometeorological techniques, and physical, chemical, and biological processes controlling air-sea fluxes were quantified with measurements in the upper ocean and marine air. Average wind speeds of 9 m s-1 to a maximum of 16 m s-1 were encountered during the tracer patch observations, providing additional data to constrain wind speed/gas exchange parameterizations. In this paper, we set the stage for the experiment by detailing the hydrographic observations during the site surveys and tracer patch occupations that form the underpinning of observations presented in the SO GasEx special section. Particular consideration is given to the mixed layer depth as this is a critical variable for estimates of fluxes and biogeochemical transformations based on mixed layer budgets.

  61. Ho, D.T., R. Wanninkhof, P. Schlosser, D.S. Ullman, D. Hebert, and K.F. Sullivan. Towards a universal relationship between wind speed and gas exchange: Gas transfer velocities measured with 3He/SF6 during the Southern Ocean Gas Exchange Experiment. Journal of Geophysical Research, 116:C00F04, 13 pp., doi:10.1029/2010JC006854 2011

    Abstract:

    Two 3He/SF6 dual-gas tracer injections were conducted during the Southern Ocean Gas Exchange Experiment (SO GasEx) to determine gas transfer velocities. During the experiment, wind speeds of up to 16.4 m s-1 were encountered. A total of 360 3He and 598 SF6 samples were collected at 40 conductivity-temperature-depth (CTD) rosette casts and two pumped stations. The gas transfer velocity k was calculated from the decrease in the observed 3He/SF6 ratio using three different approaches. Discrete points of wind speed and corresponding k were obtained from the change in 3He/SF6 ratio over three time intervals. The results were also evaluated using an analytical model and a 1-D numerical model. The results from the three approaches agreed within the error of the estimates of about ±13%±15% for Patch 1 and ±4% for Patch 2. Moreover, 3He/SF6 dual-tracer results from SO GasEx are similar to those from other areas in both the coastal and open ocean and are in agreement with existing parameterizations between wind speed and gas exchange. This suggests that wind forcing is the major driver of gas exchange for slightly soluble gases in the ocean and that other known impacts are either intrinsically related to wind or have a small effect (<20% on average) on time scales of the order of days to weeks. The functionality of the wind speed dependence (quadratic or cubic) cannot be unequivocally determined from SO GasEx results.

  62. Levine, N.M., S.C. Doney, I. Lima, R. Wanninkhof, N.R. Bates, and R.A. Feely. The impact of the North Atlantic Oscillation on the uptake and accumulation of anthropogenic CO2 by North Atlantic Ocean mode waters. Global Biogeochemical Cycles, 25:GB3022, 15 pp., doi:10.1029/2010GB003892 2011

    Abstract: The North Atlantic Ocean accounts for about 25% of the global oceanic anthropogenic carbon sink. This basin experiences significant interannual variability primarily driven by the North Atlantic Oscillation (NAO). A suite of biogeochemical model simulations is used to analyze the impact of interannual variability on the uptake and storage of contemporary and anthropogenic carbon (Canthro) in the North Atlantic Ocean. Greater winter mixing during positive NAO years results in increased mode water formation and subsequent increases in subtropical and subpolar Canthro inventories. Our analysis suggests that changes in mode water Canthro inventories are primarily due to changes in water mass volumes driven by variations in water mass transformation rates rather than local air-sea CO2 exchange. This suggests that a significant portion of anthropogenic carbon found in the ocean interior may be derived from surface waters advected into water formation regions rather than from local gas exchange. Therefore, changes in climate modes, such as the NAO, may alter the residence time of anthropogenic carbon in the ocean by altering the rate of water mass transformation. In addition, interannual variability in Canthro storage increases the difficulty of Canthro detection and attribution through hydrographic observations, which are limited by sparse sampling of subsurface waters in time and space.

  63. Sabine, C.L., R.A. Feely, R. Wanninkhof, T. Takahashi, S. Khatiwala, and G.-H. Park. Global oceans: The global ocean carbon cycle. In State of the Climate in 2010, J. Blunden, D.S. Arndt, and M.O. Baringer (eds.). Bulletin of the American Meteorological Society, 92(6):S100-S105, doi:10.1175/1520-0477-92.6.S1 2011

    Abstract: No abstract.

  64. Wanninkhof, R., G.-H. Park, and G. Berberian. Oxygen Winkler titrations by NOAA/AOML in support of Deepwater Horizon spill monitoring. NOAA Technical Memorandum, OAR-AOML-99, 15 pp., 2011

    Abstract:

    This report details the measurement of oxygen (O2) by the Winkler method on the ships Nancy Foster, Ocean Veritas, Brooks McCall, Henry B. Bigelow, and Pisces in response to the oil spill of the Deepwater Horizon 252 well. Most of the data are from near the well and were obtained from July 1, 2010 to August 30, 2010. The purpose of these measurements was to assess the accuracy of the oxygen sensors on a conductivity-temperature-depth (CTD) sensor, henceforth referred to as CTD/O2, and to determine if the CTD/O2 sensor provided (low) biased readings in the presence of oil. Based on the analyses, we believe that the O2 analyses from the CTD/O2 and Winkler systems on the ships were accurate to within 2% (approximately equal to 4 µmol/l, approximately equal to 0.1 ml/l, or approximately equal to 0.15 ml/l), with exceptions listed in the following paragraph. The depression in O2 values observed by the CTD/O2 at depths of 1000-1300 m in the layer with diffuse oil were verified by the Winkler measurements and are attributed to oxidation of the oil and associated gas. Based on the Winkler measurements, we cannot conclusively recommend adjustments to the CTD/O2 data. A qualitative assessment suggests that the output of CTD/O2 sensors on the Brooks McCall and Ocean Veritas agreed with each other and with the Winkler measurements to within 2%. The CTD/O2 sensor on the Pisces appeared to read low by about 3% when compared with the Henry B. Bigelow CTD/O2 and Winkler O2 values that agreed well with each other. The Nancy Foster had the largest dataset of Winkler O2 values for comparison. These values were about 2.6 ± 2% higher than the CTD/O2 values in water depths of 100-1000 m but showed larger positive deviations of up to 10% at the surface and in deep water which we cannot explain.

  65. Wanninkhof, R., G.-H. Park, D. Chelton, and C. Risien. Impact of small-scale variability on air-sea CO2 fluxes. In Gas Transfer at Water Surfaces, S. Komori, W. McGillis, and R. Kurose (eds.). Kyoto University Press, Kyoto, 431-444, 2011

    Abstract:

    Global air-sea CO2 fluxes are commonly determined using the CO2 partial pressure difference between surface water and air (DELTApCO2), and wind speed. Numerical interpolation techniques and coarse grid spacing, typically of the order of 4°, used when estimating the global fluxes smooth out small-scale variability in wind and pCO2 fields. There is significant variability on smaller scales in these fields. In particular, wind speed is strongly affected by sea surface temperature (SST) on oceanic mesoscales. Here we provide an estimate of the impact of this small-scale variability on global CO2 fluxes utilizing a highresolution wind product, and estimates of surface water CO2 changes in response to small-scale changes in SST. The results show that, on a global scale, the annual air-sea CO2 fluxes for 1° smoothed fields is 2 to 4% greater than for 10° smoothed SST and winds fields. This suggests that, while the coarser resolution fields used in climatologies miss much of the small-to-regional scale variability in fluxes, they adequately present global and basin-scale flux estimates.

  66. Borges, A.V., S.R. Alin, F.P. Chavez, P. Vlahos, K.S. Johnson, J.T. Holt, W.M. Balch, N. Bates, R. Brainard, W.-J. Cai, C.T.A. Chen, K. Currie, M. Dai, M. DeGrandpre, B. Delille, A. Dickson, W. Evans, R.A. Feely, G.E. Friederich, G.-C. Gong, B. Hales, N. Hardman-Mountford, J. Hendee, J.M. Hernandez-Ayon, M. Hood, E. Huertas, D. Hydes, D. Ianson, E. Krasakopoulou, E. Litt, A. Luchetta, J. Mathis, W.R. McGillis, A. Murata, J. Newton, J. Olafsson, A. Omar, F.F. Perez, C. Sabine, J.E. Salisbury, R. Salm, V.V.S.S. Sarma, B. Schneider, M. Sigler, H. Thomas, D. Turk, D. Vandemark, R. Wanninkhof, and B. Ward. A global sea surface carbon observing system: Inorganic and organic carbon dynamics in coastal oceans. In Proceedings, OceanObs09: Sustained Ocean Observations and Information for Society (Volume 2), Venice, Italy, September 21-25, 2009, J. Hall, D.E. Harrison, and D. Stammer (eds.). ESA Publication, WPP-306, 20 pp., doi:10.5270/OceanObs09.cwp.07 2010

    Abstract: Coastal environments are an important component of the global carbon cycle, and probably more vulnerable than the open ocean to anthropogenic forcings. Due to strong spatial heterogeneity and temporal variability, carbon flows in coastal environments are poorly constrained. Hence, an integrated, international, and interdisciplinary program of ship-based hydrography, Voluntary Observing Ship (VOS) lines, time-series moorings, floats, gliders, and autonomous surface vessels with sensors for pCO2 and ancillary variables are recommended to better understand present day carbon cycle dynamics, quantify air-sea CO2 fluxes, and determine future long-term trends of CO2 in response to global change forcings (changes in river inputs, in the hydrological cycle, in circulation, sea-ice retreat, expanding oxygen minimum zones, ocean acidification, etc.) in the coastal oceans. Integration at the international level is also required for data archiving, management, and synthesis that will require multi-scale approaches including the development of biogeochemical models and use of remotely sensed parameters. The total cost of these observational efforts is estimated at about 50 million U.S. dollars per year.

  67. Feely, R.A., C.L. Sabine, R. Wanninkhof, S.R. Alin, E. Jewett, D.K. Gledhill, J. Dunne, P. McElhany, A.J. Sutton, D.S. Busch, F. Arzayus, B. Sunda, J. Geubtner, J. Hare, O. Vetter, and S. Hankin. Rationale and strategy for a national ocean acidification program, pp. 3-29. In NOAA Ocean and Great Lakes Acidification Research and Implementation Plan, A.J. Sutton (ed.). NOAA Special Report, 143 pp., 2010

    Abstract: No abstract.

  68. Feely, R.A., R. Wanninkhof, J. Stein, M.F. Sigler, E. Jewett, F. Arzayus, and D.K. Gledhill (NOAA Ocean Acidification Steering Committee). NOAA Ocean and Great Lakes Acidification Research and Implementation Plan. NOAA Special Report, 143 pp., 2010

    Abstract: No abstract.

  69. Garzoli, S.L., O. Boebel, H. Bryden, R.A. Fine, M. Fukasawa, S. Gladyshev, G. Johnson, M. Johnson, A. MacDonald, C.S. Meinen, H. Mercier, A. Orsi, A. Piola, S. Rintoul, S. Speich, M. Visbeck, and R. Wanninkhof. Progressing towards global sustained deep ocean observations. In Proceedings, OceanObs09: Sustained Ocean Observations and Information for Society (Volume 2), Venice, Italy, September 21-25, 2009, J. Hall, D.E. Harrison, and D. Stammer (eds.). ESA Publication, WPP-306, 12 pp., doi:10.5270/OceanObs09.cwp.34 2010

    Abstract:

    No abstract.

  70. Gledhill, D.K., T. Goedeke, K. Helmle, J. Hendee, A. Hilting, E. Jewett, B. Keller, D. Manzello, M. Miller, E. Rule, B. Sunda, and R. Wanninkhof. Southeast Atlantic and Gulf of Mexico region ocean acidification research implementation plan, pp. 77-91. In NOAA Ocean and Great Lakes Acidification Research Implementation Plan, A.J. Sutton (ed.). NOAA Special Report, 143 pp., 2010

    Abstract: No abstract.

  71. Juranek, L.W., R.C. Hamme, J. Kaiser, R. Wanninkhof, and P.D. Quay. Evidence of O2 consumption in underway seawater lines: Implications for air-sea O2 and CO2 fluxes. Geophysical Research Letters, 37:L01601, 5 pp., doi:10.1029/2009GL040423 2010

    Abstract:

    We observed O2 deficits of 0.5 to 2.0% (1 to 4 µmol/kg) in the underway seawater lines of three different ships. Deficits in O2/Ar and isotopic enrichments in dissolved O2 observed in underway seawater lines indicate a respiratory removal process. A 1% respiratory bias in underway lines would lead to a 2.5-5 µatm (2.5-5 µbar) enhancement in surface water pCO2. If an underway pCO2 bias of this magnitude affected all measurements, the global oceanic carbon uptake based on pCO2 climatologies would be 0.5-0.8 Pg/yr higher than the present estimate of 1.6 Pg/yr. Treatment of underway lines with bleach for several hours and thorough flushing appeared to minimize O2 loss. Given the increasing interest in underway seawater measurements for the determination of surface CO2 and O2 fluxes, respiration in underway seawater lines must be identified and eliminated on all observing ships to ensure unbiased data.

  72. Keul, N., J.W. Morse, R. Wanninkhof, D.K. Gledhill, and T.S. Bianchi. Carbonate chemistry dynamics of surface waters in the northern Gulf of Mexico. Aquatic Geochemistry, 16(3):337-351, doi:10.1007/s10498-010-9091-2 2010

    Abstract:

    This paper presents the results of two cruises in the northern Gulf of Mexico in 2008 that investigated local and short-term factors influencing the carbonate chemistry dynamics and saturation state with respect to aragonite (Ωaragonite) of surface seawater in this region. One cruise covered much of the northern half of the Gulf, and the other focused on the coastal zone west of the Atchafalaya Bay outlet of the Mississippi River--the region where the hypoxic dead zone occurs on the Louisiana shelf. Offshore waters (>100 m depth) exhibited only small variations in CO2 fugacity (fCO2), total alkalinity (TA), and Ωaragonite. Values were close to those typically observed in subtropical Atlantic Ocean and Caribbean Sea waters of similar salinity. However, inner shelf waters (2, TA, and Ωaragonite that were not directly related to salinity or distance from the Mississippi River plume. Changes in TA values were not the result of simple mixing of end-member freshwater and seawater TA concentrations but exhibited a minimum in values near salinity of 25. This minimum could be the result of microbial recycling across salinity gradients, biological removal of alkalinity by formation of calcium carbonate or mixing of a third end-member with a low alkalinity such as Terrebonne Bay. All waters were supersaturated with respect to aragonite. Offshore waters had an average Ωaragoniteof 3.86 with a standard deviation of only ±0.06 and inner shelf waters had a range in Ωaragonite values from 3.9 to 9.7 with a median of 4.3. Shelf water Ωaragonite values were elevated relative to the offshore as a consequence of both high TA input from Mississippi River and biological drawdown of CO2. A dominant factor controlling Ωaragonite distribution in offshore waters with relatively constant temperatures was fCO2, with higher supersaturation occurring in areas with low fCO2.

  73. Metzl, N., A. Corbiere, G. Reverdin, A. Lenton, T. Takahashi, A. Olsen, T. Johannessen, D. Pierrot, R. Wanninkhof, S.R. Olafsdottir, J. Olafsson, and M. Ramonet. Recent acceleration of the sea surface fCO2 growth rate in the North Atlantic subpolar gyre (1993-2008) revealed by winter observations. Global Biogeochemical Cycles, 24:GB4004, 13 pp., doi:10.1029/2009GB003658 2010

    Abstract:

    Recent studies based on ocean and atmospheric carbon dioxide (CO2) observations, suggesting that the ocean carbon uptake has been reduced, may help explain the increase in the fraction of anthropogenic CO2 emissions that remain in the atmosphere. Is it a response to climate change or a signal of ocean natural variability or both? Regional process analyses are needed to follow the ocean carbon uptake and to enable better attributions of the observed changes. Here, we describe the evolution of the surface ocean CO2fugacity (fCO2oc) over the period 1993–2008 in the North Atlantic subpolar gyre (NASPG). This analysis is based primarily on observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) conducted at different seasons in the NASPG between Iceland and Canada. The fCO2oc trends based on DIC and TA data are also compared with direct fCO2 measurements obtained between 2003 and 2007 in the same region. During winters 1993–2003, the fCO2oc growth rate was 3.7 (±0.6) μatm yr−1, higher than in the atmosphere, 1.8 (±0.1) μatm yr−1. This translates to a reduction of the ocean carbon uptake primarily explained by sea surface warming, up to 0.24 (±0.04) °C yr−1. This warming is a consequence of advection of warm water northward from the North Atlantic into the Irminger basin, which occurred as the North Atlantic Oscillation (NAO) index moved into a negative phase in winter 1995/1996. In winter 2001–2008, the fCO2oc rise was particularly fast, between 5.8 (±1.1) and 7.2 (±1.3) μatm yr−1 depending on the region, more than twice the atmospheric growth rate of 2.1 (±0.2) μatm yr−1, and in the winter of 2007–2008 the area was supersaturated with CO2. As opposed to the 1990s, this appears to be almost entirely due to changes in seawater carbonate chemistry, the combination of increasing DIC and decreasing of TA. The rapidfCO2oc increase was not only driven by regional uptake of anthropogenic CO2 but was also likely controlled by a recent increase in convective processes-vertical mixing in the NASPG and cannot be directly associated with NAO variability. The fCO2oc increase observed in 2001–2008 leads to a significant drop in pH of −0.069 (±0.007) decade−1.

  74. Monteiro, P.M.S., U. Schuster, M. Hood, A. Lenton, M. Metzl, A. Olsen, K. Rogers, C. Sabine, T. Takahashi, B. Tilbrook, J. Yoder, R. Wanninkhof, and A.J. Watson. A global sea surface carbon observing system: Assessment of changing sea surface CO2 and air-sea CO2 fluxes. In Proceedings, OceanObs09: Sustained Ocean Observations and Information for Society (Volume 2), Venice, Italy, September 21-25, 2009, J. Hall, D.E. Harrison, and D. Stammer (eds.). ESA Publication, WPP-306, 13 pp., doi:10.5270/OceanObs09.cwp.64 2010

    Abstract: No abstract.

  75. Park, G.-H., R. Wanninkhof, and J. Trinanes. Procedures to create near real-time seasonal air-sea CO2 flux maps. NOAA Technical Memorandum, OAR-AOML-98 (PB2010-112609), 14 pp., 2010

    Abstract:

    Seasonal air-sea carbon dioxide (CO2) flux maps were calculated from wind speed data and the difference in CO2 partial pressure between surface seawater (pCO2SW) and the overlying atmosphere. To infer the seasonal variability of global net air-sea CO2 fluxes over the last three decades, we derived the optimum subannual relationships between pCO2SW and the sea surface temperature (SST). These optimum subannual relationships accounted for the variations between pCO2SW and SST and showed significantly better correlations than previous relationships with fixed monthly boundaries. The derived algorithms were then applied to high-resolution SST data to yield changes in pCO2SW on a monthly basis. The pCO2SW values were also combined with a gas transfer velocity estimate derived from high resolution wind products to estimate seasonal fluxes. The seasonal fluxes that are calculated with a three- to six-month lag from real-time can be obtained at http://cwcgom.aoml.noaa.gov/erddap/griddap/aomlcarbonfluxes.graph. Here, we describe in detail the procedures and uncertainties of this product.

  76. Park, G.-H., R. Wanninkhof, S.C. Doney, T. Takahashi, K. Lee, R.A. Feely, C.L. Sabine, J. Trinanes, and I.D. Lima. Variability of global net sea-air CO2 fluxes over the last three decades using empirical relationships. Tellus B, 62(5):352-368, doi:10.1111/j.1600-0889.2010.00498.x 2010

    Abstract:

    The interannual variability of net sea–air CO2 flux for the period 1982–2007 is obtained from a diagnostic model using empirical subannual relationships between climatological CO2 partial pressure in surface seawater (pCO2SW) and sea surface temperature (SST), along with interannual changes in SST and wind speed. These optimum subannual relationships show significantly better correlation between pCO2SW and SST than the previous relationships using fixed monthly boundaries. Our diagnostic model yields an interannual variability of ±0.14 PgC yr−1 (1σ) with a 26-year mean of −1.48 PgC yr−1. The greatest interannual variability is found in the Equatorial Pacific, and significant variability is also found at northern and southern high-latitudes, depending in part, on which wind product is used. We provide an assessment of our approach by applying it to pCO2SW and SST output from a prognostic global biogeochemical ocean model. Our diagnostic approach applied to this model output shows reasonable agreement with the prognostic model net sea–air CO2fluxes in terms of magnitude and phase of variability, suggesting that our diagnostic approach can capture much of the observed variability on regional to global scale. A notable exception is that our approach shows significantly less variability than the prognostic model in the Southern Ocean.

  77. Peng, T.-H., and R. Wanninkhof. Increase of anthropogenic CO2 in the Atlantic Ocean in the last two decades. Deep-Sea Research, Part I, 57(6):755-770, doi:10.1016/j.dsr.2010.03.008 2010

    Abstract: Data from the first systematic survey of inorganic carbon parameters on a global scale, the GEOSECS program, are compared with those collected during WOCE/JGOFS to study the changes in carbon and other geochemical properties, and anthropogenic CO2 increase in the Atlantic Ocean from the 1970s to the early 1990s. This first data-based estimate of CO2 increase over this period was accomplished by adjusting the GEOSECS data set to be consistent with recent high-quality carbon data. Multiple Linear Regression (MLR) and extended Multiple Linear Regression (eMLR) analyses to these carbon data are applied by regressing DIC with potential temperature, salinity, AOU, silica, and PO4 in three latitudinal regions for the western and eastern basins in the Atlantic Ocean. The results from MLR (and eMLR provided in parentheses) indicate that the mean anthropogenic CO2 uptake rate in the western basin is 0.70 (0.53) mol m-2 yr-1 for the region north of 151°N; 0.53 (0.36) mol m-2 yr-1 for the equatorial region between 151°N and 151°S; and 0.83 (0.35) mol m-2 yr-1 in the South Atlantic south of 151°S. For the eastern basin an estimate of 0.57 (0.45) m-2 yr-1 is obtained for the equatorial region, and 0.28 (0.34) mol m-2 yr-1 for the South Atlantic south of 151°S. The results of using eMLR are systematically lower than those from MLR method in the western basin. The anthropogenic CO2 increase is also estimated in the upper thermocline from salinity normalized DIC after correction for AOU along the isopycnal surfaces. For these depths the results are consistent with the CO2 uptake rates derived from both MLR and eMLR methods.

  78. Pierrot, D., P. Brown, S. Van Heuven, T. Tanhua, U. Schuster, R. Wanninkhof, and R.M. Key. CARINA TCO2 data in the Atlantic Ocean. Earth System Science Data, 2(2):177-187, doi:10.5194/essd-2-177-2010 2010

    Abstract: Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 cruises in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged in a new data base: the CARINA (CARbon IN the Atlantic) Project. These data have gone through rigorous quality control (QC) procedures so as to improve the quality and consistency of the data as much as possible. Secondary quality control, which involved objective study of data in order to quantify systematic differences in the reported values, was performed for the pertinent parameters in the CARINA data base. Systematic biases in the data have been tentatively corrected in the data products. The products are three merged data files with measured, adjusted and interpolated data of all cruises for each of the three CARINA regions (Arctic Mediterranean Seas, Atlantic and Southern Ocean). Ninety-eight cruises were conducted in the Atlantic defined as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30°S. Here we report the details of the secondary QC which was done on the total dissolved inorganic carbon (TCO2) data and the adjustments that were applied to yield the final data product in the Atlantic. Procedures of quality control, including crossover analysis between stations and inversion analysis of all crossover data, are briefly described. Adjustments were applied to TCO2 measurements for 17 of the cruises in the Atlantic Ocean region. With these adjustments, the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the WOCE Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example, regional oceanic carbon inventories, uptake rates, and model validation.

  79. Sabine, C.L., R.A. Feely, R. Wanninkhof, T. Takahashi, S. Khatiwala, and G.-H. Park. The global ocean carbon cycle. In State of the Climate in 2009, D.S. Arndt, M.O. Baringer, and M.R. Johnson (eds.). Bulletin of the American Meteorological Society, 91(7):71-75, doi:10.1175/BAMS-91-7-StateoftheClimate 2010

    Abstract:

    No abstract.

  80. Tanhua, T., R. Steinfeldt, R.M. Key, P. Brown, N. Gruber, R. Wanninkhof, F. Perez, A. Kortzinger, A. Velo, U. Schuster, S. van Heuven, J.L. Bullister, I. Stendardo, M. Hoppema, A. Olsen, A. Kozyr, D. Pierrot, C. Schirnick, and D.W.R. Wallace. Atlantic Ocean CARINA data: Overview and salinity adjustments. Earth System Science Data, 2(1):17-34, doi:10.5194/essd-2-17-2010 2010

    Abstract: Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruise data sets in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon dioxide IN the Atlantic Ocean). The data have gone through rigorous quality control procedures to assure the highest possible quality and consistency. The data for the pertinent parameters in the CARINA database were objectively examined in order to quantify systematic differences in the reported values, i.e., secondary quality control. Systematic biases found in the data have been corrected in the three data products: merged data files with measured, calculated, and interpolated data for each of the three CARINA regions, i.e., the Arctic Mediterranean Seas, the Atlantic and the Southern Ocean. These products have been corrected to be internally consistent. Ninety-eight of the cruises in the CARINA database were conducted in the Atlantic Ocean, defined here as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30°S. Here we present an overview of the Atlantic Ocean synthesis of the CARINA data and the adjustments that were applied to the data product. We also report the details of the secondary QC (Quality Control) for salinity for this data set. Procedures of quality control, including crossover analysis between stations and inversion analysis of all crossover data, are briefly described. Adjustments to salinity measurements were applied to the data from 10 cruises in the Atlantic Ocean region. Based on our analysis we estimate the internal consistency of the CARINA-ATL salinity data to be 4.1 ppm. With these adjustments the CARINA data products are consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

  81. Wanninkhof, R., S.C. Doney, J.L. Bullister, N.M. Levine, M. Warner, and N. Gruber. Detecting anthropogenic CO2 changes in the interior Atlantic Ocean between 1989 and 2005. Journal of Geophysical Research, 115:C11028, 25 pp., doi:10.1029/2010JC006251 2010

    Abstract:

    Repeat observations along the meridional Atlantic section A16 from Iceland to 56°S show substantial changes in the total dissolved inorganic carbon (DIC) concentrations in the ocean between occupations from 1989 through 2005. The changes correspond to the expected increase in DIC driven by the uptake of anthropogenic CO2 from the atmosphere, but the Δ-DIC is more varied and larger, in some locations, than can be explained solely by this process. Concomitant large changes in oxygen (O2) suggest that processes acting on the natural carbon cycle also contribute to Δ-DIC. Precise partial pressure of CO2 measurements suggest small but systematic increases in the bottom waters. To isolate the anthropogenic CO2 component (Δ-Canthro) from Δ-DIC, an extended multilinear regression approach is applied along isopycnal surfaces. This yields an average depth-integrated Δ-Canthro of 0.53 ± 0.05 mol m-2 yr-1 with maximum values in the temperate zones of both hemispheres and a minimum in the tropical Atlantic. A higher decadal increase in the anthropogenic CO2 inventory is found for the South Atlantic compared to the North Atlantic. This anthropogenic CO2 accumulation pattern is opposite to that seen for the entire Anthropocene up to the 1990s. This change could perhaps be a consequence of the reduced downward transport of anthropogenic CO2 in the North Atlantic due to recent climate variability. Extrapolating the results for this section to the entire Atlantic basin (63°N to 56°S) yields an uptake of 5 ± 1 Pg C decade-1, which corresponds to about 25% of the annual global ocean uptake of anthropogenic CO2 during this period.

  82. Chierici, M., A. Olsen, T. Johannessen, J. Trinanes, and R. Wanninkhof. Algorithms to estimate the carbon dioxide uptake in the northern North Atlantic using shipboard observations, satellite, and ocean analysis data. Deep-Sea Research, Part II, 56(8-10):630-639, doi:10.1016/j.dsr2.2008.12.014 2009

    Abstract:

    Observations of the surface-water fugacity of carbon dioxide (fCO2sw) measured during 2005 in the subpolar North Atlantic Ocean (58-62°N, 10-40°W) were used together with in-situ ocean data and remotely sensed data to develop algorithms to estimate fCO2sw. Based on multiple regression, we found that sea-surface temperature (SST), mixed-layer depth (MLD), and chlorophyll a (chl a) contributed significantly to the fit. Two algorithms were developed for periods depending on the presence of chl a data. The correlation coefficient (r2) and the root-mean-square deviation (rms) for the best fit in the period when chl a was observed (20 March-15 October) were 0.720 and ±10.8 µatm, respectively. The best fit for the algorithm for the period when no chl a was present (16 October-19 March) resulted in a r2 of 0.774 and a rms of ±5.6 µatm. Based on these algorithms, we estimated seasonal fields of fCO2sw and the air-sea CO2 flux. The estimated net annual CO2 sink was 0.0058 Gt C yr-1 or 0.6 mol C m-2 yr-1.

  83. Dickey, T., N. Bates, R.H. Byrne, G. Chang, F.P. Chavez, R.A. Feely, A.K. Hanson, D.M. Karl, D. Manov, C. Moore, C.L. Sabine, and R. Wanninkhof. The NOPP O-SCOPE and MOSEAN projects: Advanced sensing for ocean observing systems. Oceanography, 22(2):168-181, doi:10.5670/oceanog.2009.47 2009

    Abstract: The National Oceanographic Partnership Program (NOPP) consecutively sponsored the Ocean-Systems for Chemical, Optical, and Physical Experiments (O-SCOPE) and Multi-disciplinary Ocean Sensors for Environmental Analyses and Networks (MOSEAN) projects from 1998 through 2008. The O-SCOPE and MOSEAN projects focused on developing and testing new sensors and systems for autonomous, concurrent measurements of biological, chemical, optical, and physical variables from a diverse suite of stationary and mobile ocean platforms. Design considerations encompassed extended open-ocean and coastal deployments, instrument durability, biofouling mitigation, data accuracy and precision, near-real-time data telemetry, and economythe latter being critical for widespread sensor and system utilization. The complementary O-SCOPE and MOSEAN projects increased ocean sensing and data telemetry capabilities for addressing many societally relevant problems such as global climate change, ocean carbon cycling and sequestration, acidification, eutrophication, anoxia, and ecosystem dynamics, including harmful algal blooms. NOPP support enabled O-SCOPE and MOSEAN to accelerate progress in achieving multiscale, multidisciplinary, sustained observations of the ocean environment. Importantly, both programs produced value-added scientific results, which demonstrated the utility of these new technologies. The NOPP framework fostered strong collaborations among academic, commercial, and government entities, and facilitated technology transfers to the general research community and to long-term observational and observatory programs.

  84. Doney, S.C., I. Lima, R.A. Feely, D.M. Glover, K. Lindsay, N. Mahowald, J.K. Moore, and R. Wanninkhof. Mechanisms governing interannual variability in upper-ocean inorganic carbon system and air-sea CO2 fluxes: Physical climate and atmospheric dust. Deep-Sea Research, Part II, 56(8-10):640-655, doi:10.1016/j.dsr2.2008.12.006 2009

    Abstract: We quantify the mechanisms governing interannual variability in the global, upper-ocean inorganic carbon system using a hindcast simulation (1979-2004) of an ecosystem-biogeochemistry model forced with time-evolving atmospheric physics and dust deposition. We analyze the variability of three key, interrelated metrics--air-sea CO2 flux, surface-water carbon dioxide partial pressure pCO2, and upper-ocean dissolved inorganic carbon (DIC) inventory--presenting for each metric global spatial maps of the root mean square (rms) of anomalies from a model monthly climatology. The contribution of specific driving factors is diagnosed using Taylor expansions and linear regression analysis. The major regions of variability occur in the Southern Ocean, tropical Indo-Pacific, and Northern Hemisphere temperate and subpolar latitudes. Ocean circulation is the dominant factor driving variability over most of the ocean, modulating surface dissolved inorganic carbon that in turn alters surface-water pCO2 and air-sea CO2 flux variability (global integrated anomaly rms of 0.34 Pg C yr-1). Biological export and thermal solubility effects partially damp circulation-driven pCO2 variability in the tropics, while in the subtropics, thermal solubility contributes positively to surface-water pCO2 and air-sea CO2 flux variability. Gas transfer and net freshwater inputs induce variability in the air-sea CO2 flux in some specific regions. A component of air-sea CO2 flux variability (global integrated anomaly rms of 0.14 Pg C yr-1) arises from variations in biological export production induced by variations in atmospheric iron deposition downwind of dust source regions. Beginning in the mid-1990s, reduced global dust deposition generates increased air-sea CO2 outgassing in the Southern Ocean, consistent with trends derived from atmospheric CO2 inversions.

  85. Gledhill, D.K., R. Wanninkhof, and C.M. Eakin. Observing ocean acidification from space. Oceanography, 22(4):48-60, doi:10.5670/oceanog.2009.96 2009

    Abstract: Space-based observations provide synoptic coverage of surface ocean temperature, winds, sea surface height, and color useful to a wide range of oceanographic applications. These measurements are increasingly applied to monitor large-scale environmental and climate processes that can have an impact on important managed marine resources. From observing the development of harmful algal blooms using ocean color to tracking regions of thermal stress that can induce coral bleaching, satellites are routinely used for environmental monitoring. Here, we demonstrate an approach to monitoring changes in sea surface ocean chemistry in response to ocean acidification as applied to the greater Caribbean region. The method is based on regionally specific empirical algorithms derived from ongoing ship measurements applied to remotely sensed observables. This tool is important for exploring regional to basinwide trends in ocean acidification on seasonal to interannual time scales.

  86. Pierrot, D., C. Neil, K. Sullivan, R. Castle, R. Wanninkhof, H. Lueger, T. Johannessen, A. Olsen, R.A. Feely, and C.E. Cosca. Recommendations for autonomous underway pCO2 measuring systems and data reduction routines. Deep-Sea Research, Part II, 56(8-10):512-522, doi:10.1016/j.dsr2.2008.12.005 2009

    Abstract:

    In order to facilitate the collection of high quality and uniform surface water pCO2 data, an underway pCO2 instrument has been designed based on community input and is now commercially available. Along with instrumentation, agreements were reached on data reduction and quality control that can be easily applied to data from these systems by using custom-made freeware. This new automated underway pCO2 measuring system is designed to be accurate to within 0.1 μatm for atmospheric pCO2 measurements and to within 2 µatm for seawater pCO2, targeted by the scientific community to constrain the regional air-sea CO2 fluxes to 0.2 Pg C year-1. The procedure to properly reduce the underway pCO2 data and perform the steps necessary for calculation of the fugacity of CO2 from the measurements is described. This system is now widely used by the scientific community on many different types of ships. Combined with the recommended data-reduction procedures, it will facilitate producing data sets that will significantly decrease the uncertainty currently present in estimates of air-sea CO2 fluxes.

  87. Rodgers, K.B., R.M. Key, A. Gnanadesikan, J.L. Sarmiento, O. Aumont, L. Bopp, S.C. Doney, J.P. Dunne, D.M. Glover, A. Ishida, M. Ishii, A.R. Jacobson, C.L. Monaco, E. Maier-Reimer, H. Mercier, N. Metzl, F.F. Perez, A.F. Rios, R. Wanninkhof, P. Wetzel, C.D. Winn, and Y. Yamanaka. Using altimetry to help to explain patchy changes in hydrographic carbon measurements. Journal of Geophysical Research, 114(C9):C09013, 20 pp., doi:10.1029/2008JC005183 2009

    Abstract: Here we use observations and ocean models to identify mechanisms driving large seasonal to interannual variations in dissolved inorganic carbon (DIC) and dissolved oxygen (O2) in the upper ocean. We begin with observations linking variations in upper ocean DIC and O2 inventories with changes in the physical state of the ocean. Models are subsequently used to address the extent to which the relationships derived from short-timescale (6 months to 2 years) repeat measurements are representative of variations over larger spatial and temporal scales. The main new result is that convergence and divergence (column stretching) attributed to baroclinic Rossby waves can make a first-order contribution to DIC and O2 variability in the upper ocean. This results in a close correspondence between natural variations in DIC and O2 column inventory variations and sea surface height (SSH) variations over much of the ocean. Oceanic Rossby wave activity is an intrinsic part of the natural variability in the climate system and is elevated even in the absence of significant interannual variability in climate mode indices. The close correspondence between SSH and both DIC and O2 column inventories for many regions suggests that SSH changes (inferred from satellite altimetry) may prove useful in reducing uncertainty in separating natural and anthropogenic DIC signals (using measurements from Climate Variability and Predictability's CO2/Repeat Hydrography program).

  88. Sabine, C.L., R.A. Feely, R. Wanninkhof, and T. Takahashi. The global ocean carbon cycle. In State of the Climate in 2008, T.C. Peterson and M.O. Baringer (eds.). Bulletin of the American Meteorological Society, 90(8):S65-S68, doi:10.1175/BAMS-90-8-StateoftheClimate 2009

    Abstract:

    No abstract.

  89. Takahashi, T., S.C. Sutherland, R. Wanninkhof, C. Sweeney, R.A. Feely, D.W. Chipman, B. Hales, G. Friederich, F. Chavez, C. Sabine, A. Watson, D.C.E. Bakker, U. Schuster, N. Metzl, H. Yoshikawa-Inoue, M. Ishii, T. Midorikawa, Y. Nojiri, A. Kortzinger, T. Steinhoff, M. Hoppema, J. Olafsson, T.S. Arnarson, B. Tilbrook, T. Johannessen, A. Olsen, R. Bellerby, C.S. Wong, B. Delille, N.R. Bates, and H.J.W. de Baar. Climatological mean and decadal change in surface ocean pCO2 and net sea-air CO2 flux over the global oceans. Deep-Sea Research, Part II, 56(8-10):554-577, doi:10.1016/j.dsr2.2008.12.009 2009

    Abstract:

    A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) x 5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601-1622]. A time-trend analysis using deseasonalized surface water pCO2 data in portions of the North Atlantic, North and South Pacific, and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO2 over these oceanic areas has increased on average at a mean rate of 1.5 µatm y-1 with basin-specific rates varying between 1.2 ± 0.5 and 2.1 ± 0.4 µatm y-1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Niño periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO2 and the sea-air pCO2 difference over four climatic zones in the Atlantic, Pacific, Indian, and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air-sea CO2 flux is estimated using the sea-air pCO2 difference and the air-sea gas transfer rate that is parameterized as a function of (wind speed)2 with a scaling factor of 0.26. This is estimated by inverting the bomb 14C data using Ocean General Circulation models and the 1979-2005 NCEP-DOE AMIP-II Reanalysis (R-2) wind speed data. The equatorial Pacific (14°N-14°S) is the major source for atmospheric CO2, emitting about +0.48 Pg-C y-1, and the temperate oceans between 14° and 50° in the both hemispheres are the major sink zones with an uptake flux of -0.70 Pg-C y-1 for the northern and -1.05 Pg-C y-1 for the southern zone. The high-latitude North Atlantic, including the Nordic Seas and portion of the Arctic Sea, is the most intense CO2 sink area on the basis of per unit area, with a mean of -2.5 tons-C month-1 km-2. This is due to the combination of the low pCO2 in seawater and high gas exchange rates. In the ice-free zone of the Southern Ocean (50°-62°S), the mean annual flux is small (-0.06 Pg-C y-1) because of a cancellation of the summer uptake CO2 flux with the winter release of CO2 caused by deepwater upwelling. The annual mean for the contemporary net CO2 uptake flux over the global oceans is estimated to be -1.6 ± 0.9 Pg-C y-1, which includes an undersampling correction to the direct estimate of -1.4 ± 0.7 Pg-C y-1. Taking the pre-industrial steady-state ocean source of 0.4 ± 0.2 Pg-C y-1 into account, the total ocean uptake flux including the anthropogenic CO2 is estimated to be -2.0 ± 1.0 Pg-C y-1 in 2000.

  90. Telszewski, M., A. Chazottes, U. Schuster, A.J. Watson, C. Moulin, D.C.E. Bakker, M. Gonzalez-Davila, T. Johannessen, A. Kortzinger, H. Lueger, A. Olsen, A. Omar, X.A. Padin, A.F. Rios, T. Steinhoff, M. Santana-Casiano, D.W.R. Wallace, and R. Wanninkhof. Estimating the monthly pCO2 distribution in the North Atlantic using a self-organizing neural network. Biogeosciences, 6(8):1405-1421, doi:10.5194/bg-6-1405-2009 2009

    Abstract:

    Here we present monthly, basin-wide maps of the partial pressure of carbon dioxide (pCO2) for the North Atlantic on a 1° latitude by 1° longitude grid for years 2004 through 2006 inclusive. The maps have been computed using a neural network technique which reconstructs the non-linear relationships between three biogeochemical parameters and marine pCO2. A self organizing map (SOM) neural network has been trained using 389,000 triplets of the SeaWiFS-MODIS chlorophyll-a concentration, the NCEP/NCAR reanalysis sea surface temperature, and the FOAM mixed layer depth. The trained SOM was labelled with 137,000 underway pCO2 measurements collected in situ during 2004, 2005, and 2006 in the North Atlantic, spanning the range of 208 to 437 µatm. The root mean square error (RMSE) of the neural network fit to the data is 11.6 µatm, which equals to just above 3 per cent of an average pCO2 value in the in situ dataset. The seasonal pCO2 cycle as well as estimates of the interannual variability in the major biogeochemical provinces are presented and discussed. High resolution combined with basin-wide coverage makes the maps a useful tool for several applications such as the monitoring of basin-wide air-sea CO2 fluxes or improvement of seasonal and interannual marine CO2 cycles in future model predictions. The method itself is a valuable alternative to traditional statistical modelling techniques used in geosciences.

  91. Wanninkhof, R., W.E. Asher, D.T. Ho, C.S. Sweeney, and W.R. McGillis. Advances in quantifying air-sea gas exchange and environmental forcing. Annual Reviews in Marine Science, 1:213-244, doi:10.1146/annurev.marine.010908.163742 2009

    Abstract: The past decade has seen a substantial amount of research on air-sea gas exchange and its environmental controls. These studies have significantly advanced the understanding of processes that control gas transfer, led to higher quality field measurements, and improved estimates of the flux of climate-relevant gases between the ocean and atmosphere. This review discusses the fundamental principles of air-sea gas transfer and recent developments in gas transfer theory, parameterizations, and measurement techniques in the context of the exchange of carbon dioxide. However, much of this discussion is applicable to any sparingly soluble, non-reactive gas. We show how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations.

  92. Watson, A.J., U. Schuster, D.C.E. Bakker, N.R. Bates, A. Corbiere, M. Gonzalez-Davila, T. Friedrich, J. Hauck, C. Heinze, T. Johannessen, A. Kortzinger, N. Metzl, J. Olafsson, A. Olsen, A. Oschlies, X.A. Padin, B. Pfeil, J.M. Santana-Casiano, T. Steinhoff, M. Telszewski, A.F. Rios, D.W.R. Wallace, and R. Wanninkhof. Tracking the variable North Atlantic sink for atmospheric CO2. Science, 326(5958):1391-1393, doi:10.1126/science.1177394 2009

    Abstract: The oceans are a major sink for atmospheric carbon dioxide (CO2). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO2 sink for those ocean basins that are well covered by shipping routes.

  93. Gledhill, D.K., R. Wanninkhof, F.J. Millero, and M. Eakin. Ocean acidification of the greater Caribbean region, 1996-2006. Journal of Geophysical Research, 113(C10):C10031, 11 pp., doi:10.1029/2007JC004629 2008

    Abstract:

    The global oceans serve as the largest sustained natural sink for increasing atmospheric carbon dioxide (CO2) concentrations. As this CO2 is absorbed by seawater, it not only reacts causing a reduction in seawater pH (or acidification) but also decreases the carbonate mineral saturation state (Ω), which plays an important role in calcification for many marine organisms. Ocean acidification could affect some of the most fundamental biological and geochemical processes of the sea in coming decades. Observations obtained in situ from Volunteer Observing Ships and multiple geochemical surveys have been extended using satellite remote sensing and modeled environmental parameters to derive estimates of sea-surface alkalinity (AT) and carbon dioxide partial pressure (pCO2,sw). Pairing estimates of AT and pCO2,sw have permitted characterization of the changes in sea-surface Ω, which have transpired over the past decade throughout the Greater Caribbean Region as a consequence of ocean acidification. The results reveal considerable spatial and temporal variability throughout the region. Despite this variability, we observed a strong secular decrease in aragonite saturation state (Ωarg) at a rate of approximately -0.012 ± 0.001 Ωarg yr-1 (r2 = 0.97, P < 0.001).

  94. Jiang, L.-Q., W.-J. Cai, R. Wanninkhof, Y. Wang, and H. Lueger. Air-sea CO2 fluxes on the U.S. South Atlantic Bight: Spatial and seasonal variability. Journal of Geophysical Research, 113(C7):C07019, 17 pp., doi:10.1029/2007JC004366 2008

    Abstract:

    The partial pressure of carbon dioxide (pCO2) in surface seawater on the South Atlantic Bight (SAB) of the United States was measured during six cruises from January 2005 to May 2006. The high-resolution pCO2 data allow us to create the first maps of the sea surface pCO2 over the SAB for all seasons. Contrary to an earlier study that was based on limited spatial and seasonal coverage, this study shows that the SAB is a net sink of atmospheric CO2 on an annual basis (-0.48 ± 0.21 mol m-2 a-1). The inner shelf is a source of +1.20 ± 0.24 mol m-2 a-1, while the middle and outer shelves are sinks of -1.23 ± 0.19 and -1.37 ± 0.21 mol m-2 a-1, respectively. Seasonally, the SAB shifts from a sink for atmospheric CO2 in winter to a source in summer. The annual cycle of sea surface temperature plays a dominant role in controlling the seasonal variation of the pCO2. Wind speeds are seasonally anti-correlated with the air-sea pCO2 differences, and this is an important factor in contributing to the net annual air-sea CO2 exchange. Factors related to the estimates of CO2 fluxes in the coastal ocean, such as the choice of wind speeds, the correction of gas transfer equations with nonlinearity coefficients, the effect of diel variations of pCO2, the spatial extrapolation of the pCO2 to the nearshore area, and the seasonal interpolation, are also discussed.

  95. Levine, N.M., S.C. Doney, R. Wanninkhof, K. Lindsay, and I.Y. Fung. Impact of ocean carbon system variability on the detection of temporal increases in anthropogenic CO2. Journal of Geophysical Research, 113(C3):C03019, 16 pp., doi:10.1029/2007JC004153 2008

    Abstract:

    Estimates of temporal trends in oceanic anthropogenic carbon dioxide (CO2) rely on the ability of empirical methods to remove the large natural variability of the ocean carbon system. A coupled carbon-climate model is used to evaluate these empirical methods. Both the ΔC* and multiple linear regression (MLR) techniques reproduce the predicted increase in dissolved inorganic carbon for the majority of the ocean and have similar average percent errors for decadal differences (24.1% and 25.5%, respectively). However, this study identifies several regions where these methods may introduce errors. Of particular note are mode and deep water formation regions, where changes in air-sea disequilibrium and structure in the MLR residuals introduce errors. These results have significant implications for decadal repeat hydrography programs, indicating the need for subannual sampling in certain regions of the oceans in order to better constrain the natural variability in the system and to robustly estimate the intrusion of anthropogenic CO2.

  96. Lueger, H., R. Wanninkhof, A. Olsen, J. Trinanes, T. Johannessen, D.W.R. Wallace, and A. Kortzinger. The sea-air CO2 flux in the North Atlantic estimated from satellite and Argo profiling float data. NOAA Technical Memorandum, OAR-AOML-96, 28 pp., 2008

    Abstract:

    To improve the spatial and temporal resolution of sea-air carbon dioxide (CO2) flux estimates in the mid-latitude North Atlantic Ocean (30°N-63°N), empirical relationships were derived between the measured fugacity of CO2 in surface water (fCO2 sw), sea surface temperature (SST), and the mixed layer depth (MLD). Satellite chlorophyll was unsuccessful as a predictive parameter. The algorithms for fCO2 sw predictions were developed using Advanced Very High Resolution Radiometer (AVHRR) satellite SST and MLD data obtained from Argo floats. The root mean square (RMS) difference between the algorithms and fCO2 sw data was 9-10 µatm with a precision, determined from independent data, of 9-11 µatm. This precision is close to that necessary to constrain the sea-air flux in the mid-latitude North Atlantic Ocean to 0.1 Pg C yr-1. The algorithms were applied on high-resolution SST and MLD data to yield fCO2 sw proxy data for the entire region. The proxy data served to produce seasonal CO2 flux maps. In 2002, the mid-latitude North Atlantic was a year-round sink and took up 1.9 mol m-2 yr-1.

  97. Park, G.-H., K. Lee, R. Wanninkhof, J.-Z. Zhang, D.A. Hansell, and R.A. Feely. Large, non-Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N): Evidence for dinitrogen fixation? Limnology and Oceanography, 53(5):1697-1704, doi:10.4319/lo.2008.53.5.1697 2008

    Abstract: Considerable drawdown of total dissolved inorganic carbon (CT) and oversaturation of oxygen (O2) within a cold (15°C) oligotrophic eddy in the extratropical North Atlantic Ocean (46°N, 20.5°W) indicate that, despite the absence of nitrate (NO3), the eddy was highly productive. Estimates of net community production using the mass balances of CT and O2 were two to five times greater than those obtained using the mass balance of NO3. The remineralization rates obtained using the integrated rates of CT and NO3 accumulation and O2 utilization for the upper thermocline waters (35-300-m depth) were in agreement with CT- and O2-based net community production over the same period; however, all the estimates exceeded the NO3 -based net community production by a factor of two to five, pointing to a considerable accumulation of NO3 in the upper thermocline in excess of changes in the mixed-layer NO3 inventory. The amount of this excess NO3 suggests that a considerable fraction of the net community production was not supported by the mixed-layer NO3 inventory and that an external source of NO3 must be present. Of the various mechanisms that might explain the inequity between NO3 drawdown in the surface layer and NO3 accumulation in the upper thermocline, N2 fixation is the most viable yet surprising mechanism for producing such excess NO3 in this oligotrophic eddy. A significant fraction of net community production in oligotrophic extratropical waters could be supported by processes that are not fully explored or to date have been considered to be insignificant.

  98. Sabine, C.L., R.A. Feely, R. Wanninkhof, and T. Takahashi. Global oceans: The global ocean carbon cycle. In State of the Climate in 2007, D.H. Levinson and J.H. Lawrimore (eds.). Bulletin of the American Meteorological Society, 89(7):S52-S56, doi:10.1175/BAMS-89-7-StateoftheClimate 2008

    Abstract:

    No abstract.

  99. Thomas, H., A.E.F. Prowe, I.D. Lima, S.C. Doney, R. Wanninkhof, R.J. Greatbatch, U. Schuster, and A. Corbiere. Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past two decades. Global Biogeochemical Cycles, 22(4):GB4027, 13 pp., doi:10.1029/2007GB003167 2008

    Abstract: Observational studies report a rapid decline of ocean CO2 uptake in the temperate North Atlantic during the last decade. We analyze these findings using ocean physical-biological numerical simulations forced with interannually varying atmospheric conditions for the period 1979-2004. In the simulations, surface ocean water mass properties and CO2 system variables exhibit substantial multiannual variability on sub-basin scales in response to wind-driven reorganization in ocean circulation and surface warming/cooling. The simulated temporal evolution of the ocean CO2 system is broadly consistent with reported observational trends and is influenced substantially by the phase of the North Atlantic Oscillation (NAO). Many of the observational estimates cover a period after 1995 of mostly negative or weakly positive NAO conditions, which are characterized in the simulations by reduced North Atlantic Current transport of subtropical waters into the eastern basin and by a decline in CO2 uptake. We suggest therefore that air-sea CO2 uptake may rebound in the eastern temperate North Atlantic during future periods of more positive NAO, similar to the patterns found in our model for the sustained positive NAO period in the early 1990s. Thus, our analysis indicates that the recent rapid shifts in CO2 flux reflect decadal perturbations superimposed on more gradual secular trends. The simulations highlight the need for long-term ocean carbon observations and modeling to fully resolve multiannual variability, which can obscure detection of the long-term changes associated with anthropogenic CO2 uptake and climate change.

  100. Borges, A.V., and R. Wanninkhof. Preface: 37th International Liege Colloquium on Ocean Dynamics, Liege, Belgium, May 2-6, 2005, 5th International Symposium on Gas Transfer at Water Surfaces. Journal of Marine Systems, 66(1-4):1-3, doi:10.1016/j.jmarsys.2006.07.004 2007

    Abstract:

    No abstract.

  101. Broecker, W.S., and R. Wanninkhof. Mono Lake radiocarbon: The mystery deepens. EOS, Transactions, American Geophysical Union, 88(12):141-142, doi:10.1029/2007EO120001 2007

    Abstract:

    The ratio of carbon-14 (14C) to carbon in the dissolved inorganic carbon (SIGMA-CO2) of California's Mono Lake has continued to rise at a rate far faster than expected from the invasion of bomb-test 14C-labeled atmospheric CO2. Two explanations can be given. One is that the invasion rate of carbon dioxide from the atmosphere is 5 or so times higher than that for chemically inert gases. The second is that Mono Lake has been used as a site for clandestine disposal of radiocarbon.

  102. Chavez, F.P., T. Takahashi, W.-J. Cai, G. Friederich, B. Hales, R. Wanninkhof, and R.A. Feely. Coastal oceans. In The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. U.S. Climate Change Science Program and the Subcommittee on Global Change Research, A.W. King, L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.) NOAA-National Climatic Data Center, Asheville, NC, USA, 157-166, 2007

    Abstract:

    No abstract.

  103. McGillis, W.R., J.H. Dacey, J.D. Ware, D.T. Ho, J.T. Bent, W.E. Asher, C.J. Zappa, P.A. Raymond, R. Wanninkhof, and S. Komori. Air-water reconciliation between the atmospheric CO2 profile and mass balance techniques. In Transport at the Air-Sea Interface: Measurements, Models, and Parameterizations, C.S. Garbe, R.A. Handler, and B. Jahne (eds.). Springer-Verlag, Berlin, 181-192, 2007

    Abstract:

    Studies deploying atmospheric flux-profile techniques in laboratory wind-wave tanks have been performed to demonstrate and verify the use of air-side turbulent transport models and micrometeorological approaches to accurately determine air-water gas transfer velocities. Air-water gas transfer velocities have been estimated using the CO2 atmospheric flux-profile technique in laboratory wind-wave tanks both at the NASA Wallops Flight Facility, USA and Kyoto University, Japan. Gas fluxes using the flux-profile and the waterside mass balance techniques have been reconciled. Air-water fluxes of H2O and momentum were also measured simultaneously in a linear wind-wave tank. The waterside mass balances used the evasion of SF6. The CO2, H2O, and momentum fluxes were calculated using the atmospheric flux-profile technique over a wind speed range of 1 to 14 m s-1. The CO2 and H2O atmospheric profile model uses airside turbulent diffusivities derived from momentum fluxes. These studies demonstrate that the quantification of air-water CO2 fluxes using the atmospheric flux-profile technique can be implemented in the laboratory. The profile technique can be used to measure an air-water flux in much less time than a mass balance. Effects of surfactants, wind speed, and wind stress on air-water transfer are also explored using the flux-profile technique. Validation of the air-water CO2 gas exchange in laboratory wind-wave tanks provides evidence and support that this technique may be used in field studies.

  104. Sabine, C.L., R.A. Feely, and R. Wanninkhof. Global oceans: Global ocean carbon cycle. In State of the Climate in 2006, A. Arguez, A.M. Waple, and A.M. Sanchez-Lugo (eds.). Bulletin of the American Meteorological Society, 88(6):S40-S43, doi:10.1175/BAMS-88-6-929 2007

    Abstract:

    No abstract.

  105. Sweeney, C., E. Gloor, A.R. Jacobson, R.M. Key, G. McKinley, J.L. Sarmiento, and R. Wanninkhof. Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements. Global Biogeochemical Cycles, 21(2):GB2015, 10 pp., doi:10.1029/2006GB002784 2007

    Abstract:

    The 14CO2 released into the stratosphere during bomb testing in the early 1960s provides a global constraint on air-sea gas exchange of soluble atmospheric gases like CO2. Using the most complete database of dissolved inorganic radiocarbon, DI14C, available to date and a suite of ocean general circulation models in an inverse mode we recalculate the ocean inventory of bomb-produced DI14C in the global ocean and confirm that there is a 25% decrease from previous estimates using older DI14C data sets. Additionally, we find a 33% lower globally averaged gas transfer velocity for CO2 compared to previous estimates (Wanninkhof, 1992) using the NCEP/NCAR Reanalysis 1 1954-2000 where the global mean winds are 6.9 m s-1. Unlike some earlier ocean radiocarbon studies, the implied gas transfer velocity finally closes the gap between small-scale deliberate tracer studies and global-scale estimates. Additionally, the total inventory of bomb-produced radiocarbon in the ocean is now in agreement with global budgets based on radiocarbon measurements made in the stratosphere and troposphere. Using the implied relationship between wind speed and gas transfer velocity ks = 0.27 u102 (Sc/660)-0.5 and standard partial pressure difference climatology of CO2 we obtain an net air-sea flux estimate of 1.3 ± 0.5 PgCyr-1 for 1995. After accounting for the carbon transferred from rivers to the deep ocean, our estimate of oceanic uptake (1.8 ± 0.5 PgCyr-1) compares well with estimates based on ocean inventories, ocean transport inversions using ocean concentration data, and model simulations.

  106. Wang, Z.A., X. Liu, R.H. Byrne, R. Wanninkhof, R.E. Bernstein, E.A. Kaltenbacher, and J. Patten. Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater. Analytica Chimica Acta, 596(1):23-36, 2007

    Abstract:

    An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength of ~15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed within the bore-hole of a PEEK rod. This Teflon AF tubing is filled with a standard indicator solution with a fixed total alkalinity, and forms a liquid core waveguide (LCW). The LCW functions as both a long pathlength (~15 cm) optical cell and a membrane that equilibrates the internal standard solution with external seawater. fCO2 is then determined by measuring the pH of the internal solution. DIC is measured by determining the pH of standard internal solutions in equilibrium with seawater that has been acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ~7 samples (21 measurements) per hour. The system was used for underway measurements of sea surface pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean in 2005. The field precisions were evaluated to be 0.0008 units for pH, 0.9 µatm for fCO2, and 2.4 µmol kg-1 for DIC. These field precisions are close to those obtained in the laboratory. Direct comparison of our measurements and measurements obtained using established standard methods revealed that the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 µatm for fCO2, and 2.2 ± 6.0 µmol kg-1 for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of both seawater and freshwater.

  107. Wanninkhof, R. The impact of different gas exchange formulations and wind speed products on global air-sea CO2 fluxes. In Transport at the Air-Sea Interface: Measurements, Models, and Parameterizations, C.S. Garbe, R.A. Handler, and B. Jahne (eds.). Springer-Verlag, 1-23, doi:10.1007/978-3-540-36906-6_1 2007

    Abstract:

    Significant advances have been made over the last decade in estimating air-sea CO2 fluxes over the ocean by the bulk formulation that expresses the flux as the product of the gas transfer velocity and the concentration difference of aqueous CO2 over the liquid boundary layer. This has resulted in a believable global monthly climatology of air-sea CO2 fluxes over the ocean on a 4° by 5° grid. It is shown here that the global air-sea CO2 fluxes are very sensitive to estimates of gas transfer velocity and the parameterization of gas transfer with wind. Wind speeds can now be resolved at sufficient temporal and spatial resolution that they should not limit the estimates, but the absolute magnitudes of winds for different wind products differ significantly. It is recommended to use satellite-derived wind products that have the appropriate resolution instead of assimilated products that often do not appropriately resolve variability on sub-daily and sub-25-km space scales. Parameterizations of gas exchange with wind differ in functional form and magnitude but the difference between the most-used quadratic relationships is about 15%. Based on current estimates of uncertainty of the air-water CO2 concentration differences, the winds, and the gas exchange-wind speed parameterization, each parameter contributes similarly to the overall uncertainty in the flux that is estimated at 25%.

  108. Wanninkhof, R., A. Olsen, and J.A. Trinanes. Air-sea CO2 fluxes in the Caribbean Sea from 2002-2004. Journal of Marine Systems, 66(1-4):272-284, doi:10.1016/j.jmarsys.2005.11.014 2007

    Abstract:

    Air-sea fluxes in the Caribbean Sea are presented based on measurements of partial pressure of CO2 in surface seawater, pCO2sw, from an automated system onboard the cruise ship Explorer of the Seas for 2002 through 2004. The pCO2sw values are used to develop algorithms of pCO2sw based on sea surface temperature (SST) and position. The algorithms are applied to assimilated SST data and remotely sensed winds on a 1° by 1° grid to estimate the fluxes on weekly timescales in the region. The positive relationship between pCO2sw and SST is lower than the isochemical trend, suggesting counteracting effects from biological processes. The relationship varies systematically with location with a stronger dependence further south. Furthermore, the southern area shows significantly lower pCO2sw in the fall compared to the spring at the same SST, which is attributed to differences in salinity. The annual algorithms for the entire region show a slight trend between 2002 and 2004, suggesting an increase of pCO2sw over time. This is in accord with the increasing pCO2sw due to the invasion of anthropogenic CO2. The annual fluxes of CO2 yield a net invasion of CO2 to the ocean that ranges from -0.04 to -1.2 mol m-2 year-1 over the three years. There is a seasonal reversal in the direction of the flux with CO2 entering into the ocean during the winter and an evasion during the summer. Year-to-year differences in flux are primarily caused by temperature anomalies in the late winter and spring period resulting in changes in invasion during these seasons. An analysis of pCO2sw before and after Hurricane Frances (September 4-6, 2004), and wind records during the storm suggest a large local enhancement of the flux but minimal influence on annual fluxes in the region.

  109. Feely, R.A., R. Wanninkhof, C.L. Sabine, G.C. Johnson, M.O. Baringer, J. Bullister, C.W. Mordy, and J.-Z. Zhang. Global repeat hydrographic/CO2/tracer surveys in support of CLIVAR and global carbon cycle objectives: Carbon inventories and fluxes, pp. 196-205. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate (FY-2005), J.M. Levy, D.M. Stanitski, and P. Arkin (eds.). NOAA Office of Climate Observation, Silver Spring, MD, 337 pp., 2006

    Abstract:

    No abstract.

  110. Feely, R.A., T. Takahashi, R.H. Wanninkhof, M.J. McPhaden, C.E. Cosca, S.C. Sutherland, and M.-E. Carr. Decadal variability of the air-sea CO2 fluxes in the equatorial Pacific Ocean. Journal of Geophysical Research, 111(C8):C08S90, 16 pp., doi:10.1029/2005JC003129 2006

    Abstract:

    In order to determine the interannual and decadal changes in the air-sea carbon fluxes of the equatorial Pacific, we developed seasonal and interannual relationships between the fugacity of CO2 (fCO2) and sea surface temperature (SST) from shipboard data that were applied to high-resolution temperature fields deduced from satellite data to obtain high-resolution large-scale estimates of the regional fluxes. The data were gathered on board research ships from November 1981 through June 2004 between 95°W and 165°E. The distribution of fCO2sw during five El Niño periods and four La Niña periods were documented. Observations made during the warm boreal winter-spring season and during the cooler boreal summer-fall season of each year enabled us to examine the interannual and seasonal variability of the fCO2sw-SST relationships. A linear fit through all of the data sets yields an inverse correlation between SST and fCO2sw, with both interannual and seasonal differences in slope. On average, the surface water fCO2 in the equatorial region has been increasing at a rate similar to the atmospheric CO2 increase. In addition, there appears to be a slight increase (~27%) in the outgassing flux of CO2 after the 1997-1998 Pacific Decadal Oscillation (PDO) regime shift. Most of this flux increase is due to increase in wind speeds after the spring of 1998, although increases in fCO2sw after 1998 are also important. These increases are coincident with the recent rebound of the shallow water meridional overturning circulation in the tropical and subtropical Pacific after the regime shift.

  111. Lee, K., L.T. Tong, F.J. Millero, C.L. Sabine, A.G. Dickson, C. Goyet, G.-H. Park, R. Wanninkhof, R.A. Feely, and R.M. Key. Global relationships of total alkalinity with salinity and temperature in surface waters of the world's oceans. Geophysical Research Letters, 33(19):L19605, 5 pp., doi:10.1029/2006GL027207 2006

    Abstract:

    A simple function of sea surface salinity (SSS) and temperature (SST) in the form AT = a + b (SSS - 35) + c (SSS - 35)2 + d (SST - 20) + e (SST - 20)2 fits surface total alkalinity (AT) data for each of five oceanographic regimes within an area-weighted uncertainty of ±8.1 µmol kg-1 (1 sigma). Globally coherent surface AT data (n = 5,692) used to derive regional correlations of AT with SSS and SST were collected during the global carbon survey in the 1990s. Such region-specific AT algorithms presented herein enable the estimation of the global distribution of surface AT when observations of SSS and SST are available.

  112. Lueger, H., R.H. Wanninkhof, D.W.R. Wallace, and A. Kortzinger. CO2 fluxes in the subtropical and subarctic North Atlantic based on measurements from a volunteer observing ship. Journal of Geophysical Research, 111(6):C06024, 10 pp., doi:10.1029/2005JC003101 2006

    Abstract:

    Surface seawater pCO2 and related parameters were measured at high frequency onboard the volunteer observing ship M/V Falstaff in the North Atlantic Ocean between 36° and 52°N. Over 90,000 data points were used to produce monthly CO2 fluxes for 2002/2003. The air-sea CO2 fluxes calculated by two different averaging schemes were compared. The first approach used gas transfer velocity determined from wind speed retrieved at the location of the ship and called colocated winds, while for the second approach a monthly averaged gas transfer velocity was calculated from the wind for each grid pixel including the variability in wind. The colocated wind speeds determined during the time of passage do not capture the monthly wind speed variability of the grid resulting in fluxes that were 47% lower than fluxes using the monthly averaged wind products. The Falstaff CO2 fluxes were in good agreement with a climatology using averaged winds. Over the entire region they differed by 2-5%, depending on the time-dependent correction scheme to account for the atmospheric in increase in pCO2. However, locally the flux differences between the ship measurements and the climatology were greater, especially in regions north of 45°N, like the eastern sector. A comparison of two wind speed products showed that the annual CO2 sink is 4% less when using 6 hourly NCEP/NCAR wind speeds compared to the QuikSCAT wind speed data.

  113. McGillis, W.R., and R.H. Wanninkhof. Aqueous CO2 gradients for air-sea flux estimates. Marine Chemistry, 98(1):100-108, doi:10.1016/j.marchem.2005.09.003 2006

    Abstract:

    The concentration of gaseous carbon dioxide (CO2) in surface seawater is a fundamental control on the CO2 flux between the ocean and atmosphere. However, the concentration gradient in the aqueous mass boundary layer determines the magnitude and direction of the flux. The gradients of CO2 in the aqueous mass boundary layer cannot be measured directly and are usually inferred from partial pressures or fugacities of CO2 (fCO2) in the air and water. In addition to the fCO2, the temperatures at the top and bottom of the aqueous mass boundary layer must be known to determine the thermodynamic driving force of CO2 gas transfer. Expressing the gradient in terms of the aqueous CO2 concentration, [CO2aq], also avoids some conceptual ambiguities. In particular, expressing the CO2 as a fugacity, which is defined relative to the gas phase, when the gas exchange rate is controlled in the aqueous mass boundary layer often leads to errors in interpretation with respect to changes in boundary layer temperature. As a result, the enhanced CO2 flux caused by the cool skin effect appears to be overestimated. Apart from the difficulties estimating the temperature at the top and bottom of the aqueous mass boundary layer, the temperature dependence of solubility and fugacity of CO2 is uncertain to the degree that it can bias air-sea CO2 flux estimates. The CO2aq at the surface, [CO2aq0], is at equilibrium with the atmospheric CO2 level. As [CO2aq0] is strongly temperature dependent, it will be significantly higher at high latitude compared to low latitude, while atmospheric CO2 levels show much less of a gradient.

  114. Park, G.-H., K. Lee, R.H. Wanninkhof, and R.A. Feely. Empirical temperature-based estimates of variability in the oceanic uptake of CO2 over the past two decades. Journal of Geophysical Research, 111(C7):C07S07, 14 pp., doi:10.1029/2005JC003090 2006

    Abstract:

    We infer the year-to-year variability of net global air-sea CO2 fluxes from observed interannual changes in wind speed and estimated differences in CO2 partial pressure between surface seawater (pCO2SW) and the overlying atmosphere. Changes in pCO2SW are estimated from changes in sea surface temperature via seasonal algorithms that relate pCO2SW to sea surface temperature. Our diagnostic model yields an interannual variability of ±0.18 petagrams (1-sigma, Pg = 1015 grams) of carbon per year for the period 1982-2001. El Niño Southern Oscillation-induced changes in the equatorial efflux contribute approximately 70% of the diagnostic modeled global variability. Regional flux anomalies for areas outside the equatorial Pacific are found to neither systematically reinforce nor counteract each other during times of transition from El Niño years to normal years. The interannual variability of ±0.18 Pg C yr-1 obtained in the present work is at the low end of previous estimates that falls in the range of ±0.2 to ±0.5 Pg C yr-1. Of the previous estimates, lower values are generally estimated from global ocean circulation-biogeochemical models, while higher values are derived from atmospheric inversion models constrained by atmospheric CO2 observations. Comparisons of our modeled results with two time series data sets and equatorial Pacific data suggest that our diagnostic model is not able to capture the full range of pCO2SW variations; this is probably due to the inability of the empirical model to fully account for changes in surface pCO2SW related to ocean biological and physical processes. The small interannual variability in our modeled fluxes suggests that observed year-to-year variations in the rate of atmospheric CO2 increase are primarily caused by changes in the rate of CO2 uptake by the land biosphere.

  115. Russell, J.L., C. Sweeney, A. Gnanadesikan, R.A. Feely, and R. Wanninkhof. Optimal network design to detect spatial patterns and variability of ocean carbon sources and sinks from underway surface pCO2 measurements, pp. 229-231. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate (FY-2005), J.M. Levy, D.M. Stanitski, and P. Arkin (eds.). NOAA Office of Climate Observation, Silver Spring, MD, 337 pp., 2006

    Abstract:

    No abstract.

  116. Sabine, C.L., R.A. Feely, and R. Wanninkhof. The global ocean carbon cycle: Inventories, sources, and sinks, pp. 97-104. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate (FY-2005), J.M. Levy, D.M. Stanitski, and P. Arkin (eds.). NOAA Office of Climate Observation, Silver Spring, MD, 337 pp., 2006

    Abstract:

    The ocean plays a major role in the global carbon cycle. Long-term (decadal) changes in ocean carbon inventory are examined by repeating measurements that are made along specific cruise tracks at intervals of 5-15 years. Recent cruises have suggested that the relative role of the Pacific versus the Atlantic storage of CO2 has changed over the last decade. Shorter-term (daily to inter-annual) changes in ocean carbon uptake are examined with sea-air CO2 flux estimates from instruments deployed on ships and moorings. The growing surface CO2 data set also indicates that there is significant interannual variability in the sea-air CO2 flux.

  117. Sabine, C.L., R.A. Feely, and R.H. Wanninkhof. Global oceans: Ocean carbon. In State of the Climate in 2005, K.A. Shein, A.M. Waple, H.J. Diamond, and J.M. Levy (eds.). Bulletin of the American Meteorological Society, 87(6):S29-S30, doi:10.1175/BAMS-87-6-801 2006

    Abstract:

    No abstract.

  118. Takahashi, T., S.C. Sutherland, R.A. Feely, and R.H. Wanninkhof. Decadal change of the surface water pCO2 in the North Pacific: A synthesis of 35 years of observations. Journal of Geophysical Research, 111(C7):C07S05, 20 pp., doi:10.1029/2005JC003074 2006

    Abstract:

    Surface water pCO2 data observed over the three decades between 1970 and 2004 are analyzed for space and time (mean decadal) variability in 32 10° x 10° box areas over the North Pacific Ocean north of 10°N. During this period, the pCO2 values at SST increased at a mean decadal rate of 12.0 ± 4.8 µatm decade-1 in all but four areas located in the vicinity of the Bering and Okhotsk Seas, where they decreased at a mean rate of -11.1 ± 5.7 µatm decade-1. The mean rate of increase for the open ocean areas is indistinguishable from the mean atmospheric CO2 increase rate of 15 µatm decade-1 (or 1.5 ppm yr-1) suggesting that the North Pacific surface waters as a whole have been following the atmospheric CO2 increase. However, the rate of increase varies geographically, reflecting differences in local oceanographic processes including lateral mixing of waters from marginal seas, upwelling of subsurface waters and biological activities. The decrease observed in the southern Bering Sea and the peripheries of the Okhotsk Sea may be accounted for by the combined effects of intensified biological production and changes in lateral and vertical mixing in these areas. The natural logarithm of wintertime pCO2 values normalized to a constant temperature and salinity of 14.3°C and 34.0 (the basin mean values, respectively) is correlated with winter SST. Using this relationship, the wintertime TCO2 in mixed layer can be expressed as a function of winter SST with a standard error of ±5 µmol kg-1.

  119. Wanninkhof, R., R.A. Feely, N.R. Bates, F.J. Millero, T. Takahashi, and S. Cook. Document ocean carbon sources and sinks: Surface water pCO2 measurements from ships, pp. 207-215. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate (FY-2005), J.M. Levy, D.M. Stanitski, and P. Arkin (eds.). NOAA Office of Climate Observation, Silver Spring, MD, 337 pp., 2006

    Abstract:

    No abstract.

  120. Arnold, W.S., G.L. Hitchcock, M.E. Frischer, R. Wanninkhof, and Y.P. Sheng. Dispersal of an introduced larval cohort in a coastal lagoon. Limnology and Oceanography, 50(2):587-597, doi:10.4319/lo.2005.50.2.0587 2005

    Abstract:

    Patterns of larval dispersal influence the structure of marine biological communities, but many aspects of larval dispersal remain poorly understood. For example, much of our present understanding of larval dispersal is based on models that integrate aspects of physical oceanography and larval biology, but the predictions of those models are generally not tested because we lack the methodology for real-time larval tracking. In the present study, we used both modeled and measured data to track an introduced larval cohort essentially from fertilization to presumed settlement. Larvae of the hard clam Mercenaria were released into a labeled water parcel in the Banana River Lagoon, Florida, within 8.5 hours of nursery production and then were tracked for the duration of their estimated 8-day pelagic life span. Comparisons of modeled versus measured larval distribution indicate that the fate of the larvae as predicted by a tracer model and by the concentration of coincidentally released sulfur hexafluoride (SF6) did not agree with the fate of the larvae as predicted by the path of subsurface drifters and by a particle trajectory model. Thus, modeled predictions of larval dispersal must be interpreted with care. Additionally, one component of larval dispersal that was observed in the study but that was not accounted for in the model was the spread of larvae along the path of advection. That trail of larvae may have important consequences for patterns of recruitment and resultant community structure, but it is not considered in most treatments of larval dispersal.

  121. Feely, R.A., and R. Wanninkhof. Global repeat hydrographic/CO2/tracer surveys in support of CLIVAR and global carbon cycle objectives: Carbon inventories and fluxes, pp. 149-168. In Annual Report on the State of the Ocean and Ocean Observing System for Climate (FY-2004), D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 422 pp., 2005

    Abstract:

    No abstract.

  122. Feely, R.A., and R. Wanninkhof. The global ocean carbon cycle: Inventories, sources, and sinks, pp. 42-56. In Annual Report on the State of the Ocean and Ocean Observing System for Climate (FY-2004), D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 422 pp., 2005

    Abstract:

    The ocean plays a major role in the global carbon cycle as it is a vast reservoir of carbon, naturally exchanges carbon with the atmosphere, and consequently takes up a substantial portion of anthropogenic carbon from the atmosphere. In response to the need for an integrated investigation of the carbon cycle in the oceans, the CLIVAR/CO2 Repeat Hydrography and NOAA Underway pCO2 Measurements Programs were established to document the trends in carbon uptake and transport in the global oceans. The CLIVAR/CO2 Repeat Hydrography Program consists of a systematic re-occupation of select hydrographic sections to quantify global changes in storage and transport of heat, fresh water, carbon dioxide (CO2), chlorofluorocarbon tracers and related parameters. Three North Atlantic cruises in 2003 marked the beginning of the U.S. effort by reoccupying selected hydrographic sections on decadal time-scales. Early results from these cruises showed significant changes in oxygen and carbon dioxide and several other measurable parameters since the last global survey in the 1990s. The increases of DIC in the Subtropical Mode waters (STMW) are greater than expected from invasion of anthropogenic CO2 from the atmosphere and may be the result of decadal changes in the local circulation in the North Atlantic.

  123. Feely, R.A., L.D. Talley, G.C. Johnson, C.L. Sabine, and R.H. Wanninkhof. Repeat hydrography cruises reveal chemical changes in the North Atlantic. EOS, Transactions, American Geophysical Union, 86(42):399-405, doi:10.1029/2005EO420003 2005

    Abstract:

    The U.S. contribution to a large international effort to document long-term trends in carbon storage and transport in the global oceans by reoccupying selected hydrographic sections on decadal timescales began with three North Atlantic cruises in 2003. The initial results from these reoccupation cruises have shown significant long-term changes in oxygen, carbon dioxide (CO2), and several other measurable parameters since the last global survey, which occurred in 1993. The ocean has a memory of the climate system and is second only to the Sun in affecting variability in the seasons and long-term climate change. The ocean stores an estimated 1000 times more heat than the atmosphere, and 50 times more carbon. Additionally, the key to possible abrupt climate change may lie in deep-ocean circulation.

  124. McNeil, C., D. Katz, R. Wanninkhof, and B. Johnson. Continuous shipboard sampling of gas tension, oxygen, and nitrogen. Deep-Sea Research, Part I, 52(9):1767-1785, doi:10.1016/j.dsr.2005.04.003 2005

    Abstract:

    A novel shipboard gas tension device (GTD) that measures total dissolved air pressure in ocean surface waters is described and demonstrated. In addition, an improved method to estimate dissolved N2 levels from simultaneous measurements of gas tension, dissolved O2, water temperature, and salinity is described. Other than a flow-through plenum, the shipboard GTD is similar to the previously described moored-mode GTD (McNeil et al., 1995, Deep-Sea Research, Part I, 42:819-826). The plenum has an integrated water-side screen to protect the membrane and prevent the membrane from flexing in super-saturated near surface waters. The sampling scheme uses a well mixed and thermally insulated 15 L container that is flushed by the ship's seawater intake at a rate of 3-15 L min-1. Dissolved gas sensors are placed inside this container and flushed with a small recirculation pump. Laboratory data that characterize the response of the modified GTD are presented. The modified GTD has a constant, isothermal, characteristic (e-folding) response time of typically 11±2 min at 20°C. The response time decreases with increasing temperature and varies by ±35% over a temperature range of 5-35°C. Results of field measurements, collected on the R/V Brown between New York and Puerto Rico during September 2002, are presented and provide the first look at co-variability in surface ocean N2, O2, and CO2 levels over horizontal length scales of several kilometers. Dissolved N2 concentrations decreased by approximately 16% as the ship sailed from the colder northern continental shelf waters, across the Gulf Stream, and into the warmer northwestern Atlantic Ocean. Historical database measurements, buoy time series, and satellite imagery, are used to aid interpretation of the dissolved gas levels.

  125. Olsen, A., R. Wanninkhof, J.A. Trinanes, and T. Johannessen. The effect of wind speed products and wind speed-gas exchange relationships on interannual variability of the air-sea CO2 gas transfer velocity. Tellus B, 57(2):95-106, doi:10.1111/j.1600-0889.2005.00134.x 2005

    Abstract:

    The lack of a firm relationship between wind speed (U10) and gas transfer velocity (k) is considered to be one of the factors that hinders accurate quantification of interannual variations of ocean-atmosphere CO2 fluxes. In this paper, the interannual variations of k of using four different k-U10 parameterizations are examined using wind speed data from the NCEP/NCAR reanalysis project. The extent to which interannual variations are faithfully reproduced in the NCEP/NCAR data is also investigated. This is carried out through comparison with QuikSCAT data. Compared with 4 years of QuikSCAT data, NCEP/NCAR data reproduce interannual k variations, although the absolute magnitude of k is underestimated. Interannual k variation shows great sensitivity to selection of k-U10 parameterization, and in the Westerlies it changes by a factor of three depending on k-U10 parameterization. Use of monthly mean winds speeds leads to overestimation of interannual k variations compared with k variations computed using 6-hourly wind speeds and the appropriate k-U10 parameterization. Even though the effect of changing k-U10 parameterization is large enough to be an issue that needs to be considered when computing interannual air-sea CO2 flux variations through combining estimates of k with data for the air-sea CO2 gradient, it is not sufficient to bridge the gap between such estimates and estimates based on analyses of atmospheric oxygen, CO2, and delta13C data. Finally, it is shown that the ambiguity in the relationship between wind speed and k introduces an uncertainty in interannual flux variations comparable to a bias of interannual DELTApCO2 variations of at most ?5 µatm.

  126. Peltola, E., R. Wanninkhof, R. Feely, R. Castle, D. Greeley, J.-Z. Zhang, F. Millero, N. Gruber, J. Bullister, and T. Graham. Inorganic carbon, nutrient, and oxygen data from the R/V Ronald H. Brown repeat hydrography cruise in the Atlantic Ocean: CLIVAR CO2 section A16N_2003a (4 June-11 August 2003). Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Technical Report, ORNL/CDIAC-149, 36 pp., 2005

    Abstract:

    This report presents methods and analytical and quality control procedures for nutrient, oxygen, and inorganic carbon system parameters performed during the A16N_2003a cruise, which took place from June 4 to August 11, 2003 aboard NOAA Ship R/V Ronald H. Brown under auspices of the National Oceanic and Atmospheric Administration (NOAA). The first hydrographic leg (June 19-July 10) was from Reykjavik, Iceland, to Funchal, Madeira, Portugal along the 20°W meridian, and the second leg (July 15-August 11) continued operations from Funchal, Portugal to Natal, Brazil, on a track southward and ending at 6°S, 25°W. The research was the first in a decadal series of repeat hydrography sections jointly funded by NOAA and the National Science Foundation (NSF) as part of the CLIVAR/CO2/hydrography/tracer program. Samples were taken from up to 34 depths at 150 stations. The data presented in this report includes the analyses of water samples for total inorganic carbon (TCO2), fugacity of CO2 (fCO2), total alkalinity (TALK), pH, nitrate (NO3), nitrite (NO2), phosphate (PO4), silicate (SiO4), and dissolved oxygen (O2). The R/V Ronald H. Brown A16N_2003a data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center (CDIAC). The NDP consists of the oceanographic data files and this printed documentation, which describes the procedures and methods used to obtain the data.

  127. Sabine, C.L., R.M. Key, A. Kozyr, R.A. Feely, R. Wanninkhof, F.J. Millero, T.-H. Peng, J.L. Bullister, and K. Lee. Global ocean data analysis project (GLODAP): Results and data. Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Technical Report, ORNL/CDIAC-145, 110 pp., 2005

    Abstract:

    During the 1990s, ocean sampling expeditions were carried out as part of the World Ocean Circulation Experiment, the Joint Global Ocean Flux Study, and the Ocean Atmosphere Carbon Exchange Study. Most of the cruises included various inorganic carbon species among the suite of routinely measured parameters. Both during and after the field work, a group of U.S. scientists collaborated to synthesize the data into easily usable and readily available products. This collaboration is known as the Global Ocean Data Analysis Project (GLODAP). Both measured results and calculated quantities were merged into common-format data sets, segregated by ocean. The carbon data were subjected to rigorous secondary quality control procedures, beyond those typically performed on individual cruise data, to eliminate systematic biases in the basin-scale compilations. For comparison purposes, each ocean data set included results from a small number of high-quality historical cruises. The calibrated 1990s data were used to estimate anthropogenic CO2, potential alkalinity, chlorofluorocarbon (CFC) water mass ages, CFC partial pressure, bomb-produced radiocarbon, and natural radiocarbon. The calibrated-merged data were used to produce objectively gridded global property maps designed to match existing climatologies for temperature, salinity, oxygen, and nutrients. Both the data sets and the gridded products are available from the Carbon Dioxide Information Analysis Center (CDIAC). Here we summarize important details of the data assembly, calibration, calculations, and mapping. The synthesis was carried out one ocean at a time, progressing from the Indian to the Pacific and ending with the Atlantic. The entire synthesis required about five years. During that period, new methods were developed and old ones modified. At the same time, the data set itself changed and expanded. Many of the GLODAP results are already published. Rather than repeat what is published, we concentrate here on summarizing important details of the data assembly and mapping. In particular, we focus on the procedural differences that evolved as the individual basin data sets were compiled and developments in the data set that have not been covered in the individual publications. Some of the GLODAP publications are attached as appendices. The GLODAP data set described here (Gv1.1) is available free of charge as a numeric data package (NDP-83) from CDIAC. The data, and any subsequent updates, are also available through the GLODAP web site (http://cdiac.ornl.gov/oceans/glodap/Glodap_home.htm). The GLODAP bottle data files are available in flat ASCII file data format, in Ocean Data View (ODV) format, and through the CDIAC live access server (LAS); the gridded data files are available in flat ASCII and NetCDF data file formats and through CDIAC LAS.

  128. Wanninkhof, R., R.A. Feely, N.R. Bates, F.J. Millero, T. Takahashi, and S.K. Cook. Document ocean carbon sources and sinks, pp. 254-262. In Annual Report on the State of the Ocean and Ocean Observing System for Climate (FY-2004), D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 422 pp., 2005

    Abstract:

    No abstract.

  129. Wanninkhof, R.H., K.F. Sullivan, W.P. Dammann, J.R. Proni, F. Bloetscher, A.V. Soloviev, and T.P. Carsey. Farfield tracing of a point source discharge plume in the coastal ocean using sulfur hexafluoride. Environmental Science and Technology, 39(22):8883-8890, doi:10.1021/es048126+ 2005

    Abstract:

    Pathways and dilution of a point source ocean discharge in the farfield (approximately equal to 10-66 km) were measured using the deliberate tracer sulfur hexafluoride (SF6). The injection of SF6 was performed by bubbling the gas over a period of 6 days into an ocean outfall pipe discharging into the southeast Florida coastal ocean. The surface SF6 concentrations show that the discharged water flowed northward parallel to the coast with a broadening of the width of the plume to about 3 km at the farthest point sampled, 66 km from the outfall. The discharge was fully mixed throughout the water column within 13 km of the outfall terminus. In the first 20 km from the outfall, SF6 surface concentrations were highly variable, while beyond this the SF6 concentrations decreased monotonically going northward. The currents were measured during the study with a bottom-mounted acoustic Doppler current profiler (ADCP) located 5.5 km from the outfall. Velocities were variable in magnitude and direction but showed a net northward flow during the 6-day study. Maximum concentrations decreased by about 200-fold per kilometer from the outfall to the northern end of the study area. The study shows that SF6 is an effective method to trace point source releases far from their origin.

  130. Wanninkhof, R.H., S.C. Doney, E. Peltola, R.D. Castle, F.J. Millero, J.L. Bullister, D.A. Hansell, M.J. Warner, C. Langdon, G.C. Johnson, and C.W. Mordy. Carbon dioxide, hydrographic, and chemical data obtained during the R/V Ronald H. Brown repeat hydrography cruise in the Atlantic Ocean: CLIVAR CO2 section A16S_2005 (11 January-24 February 2005). Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Oak Ridge, Technical Report, ORNL/CDIAC-151, 38 pp., 2005

    Abstract:

    This report presents methods, and analytical and quality control procedures for salinity, oxygen, nutrient, inorganic carbon, organic carbon, chlorofluorocarbon (CFC), and bomb 14C system parameters performed during the A16S_2005 cruise, which took place from January 11 to February 24, 2005, aboard research vessel (R/V) Ronald H. Brown under the auspices of the National Oceanic and Atmospheric Administration (NOAA). The R/V Ronald H. Brown departed Punta Arenas, Chile, on January 11, 2005, and ended its cruise in Fortaleza, Brazil, on February 24, 2005. The research conducted was one of a series of repeat hydrography sections jointly funded by NOAA and the National Science Foundation as part of the CLIVAR/CO2/Repeat Hydrography/Tracer Program. Samples were taken from 36 depths at 121 stations. The data presented in this report include the analyses of water samples for total inorganic carbon (TCO2), fugacity of CO2 (fCO2), total alkalinity (TALK), pH, dissolved organic carbon (DOC), CFC, 14C, hydrographic, and other chemical measurements. The R/V Ronald H. Brown A16S_2005 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center (CDIAC). The NDP consists of the oceanographic data files and this printed documentation, which describes the procedures and methods used to obtain the data.

  131. Coale, K.H., K.S. Johnson, F.P. Chavez, K.O. Buesseler, R.T. Barber, M.A. Brzezinski, W.P. Cochlan, F.J. Millero, P.G. Falkowski, J.E. Bauer, R.H. Wanninkhof, R.M. Kudela, M.A. Altabet, B.E. Hales, T. Takahashi, M.R. Landry, R.R. Bidigare, X. Wang, Z. Chase, P.G. Strutton, G.E. Friederich, M.Y. Gorbunov, V.P. Lance, A.K. Hilting, M.R. Hiscock, M. Demarest, W.T. Hiscock, K.F. Sullivan, S.J. Tanner, R.M. Gordon, C.N. Hunter, V.A. Elrod, S.E. Fitzwater, J.L. Jones, S. Tozzi, M. Koblizek, A.E. Roberts, J. Herndon, J. Brewster, N. Ladizinsky, G. Smith, D. Cooper, D. Timothy, S.L. Brown, K.E. Selph, C.C. Sheridan, B.S. Twining, and Z.I. Johnson. Southern Ocean Iron Enrichment Experiment: Carbon cycling in high and low Si waters. Science, 304(5669):408-414, doi:10.1126/science.1089778 2004

    Abstract:

    The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide.

  132. DeGrandpre, M.D., R.H. Wanninkhof, W.R. McGillis, and P.G. Strutton. A Lagrangian study of surface pCO2 dynamics in the eastern equatorial Pacific Ocean. Journal of Geophysical Research, 109(C8):C08S07, 9 pp., doi:10.1029/2003JC002089 2004

    Abstract:

    We characterized pCO2 variability on hourly to weekly time scales during the 14-day GasEx-2001 Lagrangian drifter experiment in the eastern equatorial Pacific Ocean. Underway pCO2 was recorded at 5 m depth as the ship closely followed a drogued drifter. Dissolved O2 (DO) was measured at 10 and 15 m depths using in situ sensors deployed on the drogue. Diel pCO2 and DO variability is evaluated using a simple model that accounts for air-sea exchange, vertical mixing, heating, and net community metabolism. Mixed-layer depths and local (vertical) entrainment are estimated with the Price Weller Pinkel (PWP) mixed-layer model. The mean observed pCO2 was 472.0 ± 1.8 µatm with a diel increase of 2-6 µatm on most days, near coincident in time with the diel peak in temperature. The biogeochemical model reveals that heating was the primary source of diel pCO2 variability, but net community production and depletion of CO2 in the shallow warm layer due to air-sea gas exchange reduced the heating-driven peak by ~1-4 and 1-2 µatm each day, respectively. The same model parameterizations also accurately predict the diel DO amplitude. In the model, atmospheric exchange depletes total CO2 and DO in the surface layer, and the depleted water is mixed with the isolated underlying water during nocturnal convection. The 10- and 15-m DO time series corroborate these predicted dynamics. Over the 14-day study, net heating offset the expected ~14 µatm decrease due to air-sea CO2 exchange and net community production, resulting in a nearly constant mean pCO2. Consequently, net heating acts to sustain high air-sea CO2 fluxes in the upwelled equatorial Pacific water as the water advects westward in the South Equatorial Current.

  133. Feely, R.A., and R.H. Wanninkhof. Document ocean carbon sources and sinks, pp. 118-120. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate, D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 307 pp., 2004

    Abstract:

    No abstract.

  134. Feely, R.A., and R.H. Wanninkhof. Global repeat hydrographic/CO2/tracer surveys in support of CLIVAR and global carbon cycle objectives, pp. 121-129. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate, D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 307 pp., 2004

    Abstract:

    No abstract.

  135. Feely, R.A., R.H. Wanninkhof, W.R. McGillis, M.-E. Carr, and C.E. Cosca. Effects of wind speed and gas exchange parameterizations on the air-sea CO2 fluxes in the equatorial Pacific Ocean. Journal of Geophysical Research, 109(C8):C08S03, 10 pp., doi:10.1029/2003JC001896 2004

    Abstract:

    During the recent GasEx-2001 cruise in the equatorial Pacific aboard the NOAA ship Ronald H. Brown, carbon measurements were made in the region of 3°S, 125°W. Continuous surface water fCO2 measurements were conducted onboard in both underway and discrete analysis modes. During the 15-day experiment, surface water fCO2 values averaged 473 ± 2 µatm, providing a constant condition of supersaturation and flux of CO2 from the ocean to the atmosphere. The relationship of gas transfer with wind speed developed in this study is used along with regional estimates of air-water fCO2 differences to determine CO2 fluxes in the equatorial Pacific. The regional fCO2 fields are estimated from algorithms developed from previous measurements collected on the Ronald H. Brown and Ka'imimoana over the past 10 years between 5°N and 10°S, 90°W and 165°E. Using the W. McGillis et al. gas transfer-wind speed relationship, we estimate an average flux of 1.5 ± 0.4 mol C m-2 yr-1 for the study region, with a six-fold difference in the regional efflux of CO2 between the strong El Niño events of 1986-1987 and 1997-1998 and the La Niña events of 1996 and 1999-2001 (i.e., 0.1 to 0.56 Pg C yr-1). The combined effects of uncertainties in the gas transfer velocity and wind fields lead to average difference of 27% between the lowest and highest estimates of the CO2 flux from the region. In contrast, the uncertainties in the fCO2-SST relationships give an average difference of about 35% between the lowest and highest estimates of the CO2 flux.

  136. Hare, J.E., C.W. Fairall, W.R. McGillis, J.B. Edson, B. Ward, and R.H. Wanninkhof. Evaluation of the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment (NOAA/COARE) air-sea gas transfer parameterization using GasEx data. Journal of Geophysical Research, 109(C8):C08S11, 11 pp., doi:10.1029/2003JC001831 2004

    Abstract:

    During the two recent GasEx field experiments, direct covariance measurements of air-sea carbon dioxide fluxes were obtained over the open ocean. Concurrently, the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment air-sea gas transfer parameterization was developed to predict gas transfer velocities from measurements of the bulk state of the sea surface and atmosphere. The model output is combined with measurements of the mean air and sea surface carbon dioxide fugacities to provide estimates of the air-sea CO2 flux, and the model is then tuned to the GasEx-1998 data set. Because of differences in the local environment and, possibly, because of weaknesses in the model, some discrepancies are observed between the predicted fluxes from the GasEx-1998 and GasEx-2001 cases. To provide an estimate of the contribution to the air-sea flux of gas due to wave-breaking processes, the whitecap and bubble parameterizations are removed from the model output. These results show that moderate (approximately 15 m s-1) wind speed breaking wave gas transfer processes account for a fourfold increase in the flux over the modeled interfacial processes.

  137. Key, R.M., A. Kozyr, C.L. Sabine, K. Lee, R. Wanninkhof, J.L. Bullister, R.A. Feely, F.J. Millero, C. Mordy, and T.-H. Peng. A global ocean carbon climatology: Results from Global Data Analysis Project (GLODAP). Global Biogeochemical Cycles, 18(4):GB40301, 23 pp., doi:10.1029/2004GB002247 2004

    Abstract:

    During the 1990s, ocean sampling expeditions were carried out as part of the World Ocean Circulation Experiment (WOCE), the Joint Global Ocean Flux Study (JGOFS), and the Ocean Atmosphere Carbon Exchange Study (OACES). Subsequently, a group of U.S. scientists synthesized the data into easily usable and readily available products. This collaboration is known as the Global Ocean Data Analysis Project (GLODAP). Results were merged into a common format data set, segregated by ocean. For comparison purposes, each ocean data set includes a small number of high-quality historical cruises. The data were subjected to rigorous quality control procedures to eliminate systematic data measurement biases. The calibrated 1990s data were used to estimate anthropogenic CO2, potential alkalinity, CFC watermass ages, CFC partial pressure, bomb-produced radiocarbon, and natural radiocarbon. These quantities were merged into the measured data files. The data were used to produce objectively gridded property maps at a 1° resolution on 33 depth surfaces chosen to match existing climatologies for temperature, salinity, oxygen, and nutrients. The mapped fields are interpreted as an annual mean distribution in spite of the inaccuracy in that assumption. Both the calibrated data and the gridded products are available from the Carbon Dioxide Information Analysis Center. Here we describe the important details of the data treatment and the mapping procedure, and present summary quantities and integrals for the various parameters.

  138. McGillis, W.R., J.B. Edson, C.J. Zappa, J.D. Ware, S.P. McKenna, E.A. Terray, J.E. Hare, C.W. Fairall, W. Drennan, M. Donelan, M.D. DeGrandpre, R.H. Wanninkhof, and R.A. Feely. Air-sea CO2 exchange in the equatorial Pacific. Journal of Geophysical Research, 109(C8):C08S02, 17 pp., doi:10.1029/2003JC002256 2004

    Abstract:

    GasEx-2001, a 15-day air-sea carbon dioxide (CO2) exchange study conducted in the equatorial Pacific, used a combination of ships, buoys, and drifters equipped with ocean and atmospheric sensors to assess variability and surface mechanisms controlling air-sea CO2 fluxes. Direct covariance and profile method air-sea CO2 fluxes were measured together with the surface ocean and marine boundary layer processes. The study took place in February 2001 near 125°W, 3°S in a region of high CO2. The diurnal variation in the air-sea CO2 difference was 2.5%, driven predominantly by temperature effects on surface solubility. The wind speed was 6.0 ± 1.3 m s-1, and the atmospheric boundary layer was unstable with conditions over the range -1 < z/L < 0. Diurnal heat fluxes generated daytime surface ocean stratification and subsequent large nighttime buoyancy fluxes. The average CO2 flux from the ocean to the atmosphere was determined to be 3.9 mol m-2 yr-1, with nighttime CO2 fluxes increasing by 40% over daytime values because of a strong nighttime increase in (vertical) convective velocities. The 15 days of air-sea flux measurements taken during GasEx-2001 demonstrate some of the systematic environmental trends of the eastern equatorial Pacific Ocean. The fact that other physical processes, in addition to wind, were observed to control the rate of CO2 transfer from the ocean to the atmosphere indicates that these processes need to be taken into account in local and global biogeochemical models. These local processes can vary on regional and global scales. The GasEx-2001 results show a weak wind dependence but a strong variability in processes governed by the diurnal heating cycle. This implies that any changes in the incident radiation, including atmospheric cloud dynamics, phytoplankton biomass, and surface ocean stratification may have significant feedbacks on the amount and variability of air-sea gas exchange. This is in sharp contrast with previous field studies of air-sea gas exchange, which showed that wind was the dominating forcing function. The results suggest that gas transfer parameterizations that rely solely on wind will be insufficient for regions with low to intermediate winds and strong insolation.

  139. McGillis, W.R., W.E. Asher, R.H. Wanninkhof, A.T. Jessup, and R.A. Feely. Introduction to special section: Air-sea exchange. Journal of Geophysical Research, 109(C8):C08S01, 2 pp., doi:10.1029/2004JC002605 2004

    Abstract:

    No abstract.

  140. Olsen, A., J.A. Trinanes, and R. Wanninkhof. Sea-air flux of CO2 in the Caribbean Sea estimated using in situ and remote sensing data. Remote Sensing of Environment, 89(3):309-325, doi:10.1016/j.rse.2003.10.011 2004

    Abstract:

    Empirical relationships between sea surface carbon dioxide fugacity (fCO2sw) and sea surface temperature (SST) were applied to data sets of remotely sensed SST to create fCO2sw fields in the Caribbean Sea. SST data sets from different sensors were used, as well as the SST fields created by optimum interpolation of bias corrected AVHRR data. Empirical relationships were derived using shipboard fCO2sw data, in situ SST data, and SST data from the remote sensing platforms. The results show that the application of a relationship based on shipboard SST data, on fields of remotely sensed SST yields biased fCO2sw values. This bias is reduced if the fCO2sw-SST relationships are derived using the same SST data that are used to create the SST fields. The fCO2sw fields found to best reproduce observed fCO2sw are used in combination with wind speed data from QuikSCAT to create weekly maps of the sea-air CO2 flux in the Caribbean Sea in 2002. The region to the southwest of Cuba was a source of CO2 to the atmosphere throughout 2002, and the region to the northeast was a sink during winter and spring and a source during summer and fall. The net uptake of CO2 in the region was doubled when potential skin layer effects on fCO2sw were taken into account.

  141. Sabine, C.L., R.A. Feely, N. Gruber, R.M. Key, K. Lee, J.L. Bullister, R.H. Wanninkhof, C.S. Wong, D.W.R. Wallace, B. Tilbrook, F.J. Millero, T.-H. Peng, A. Kozyr, T. Ono, and A.F. Rios. The oceanic sink for anthropogenic CO2. Science, 305(5682):367-371, doi:10.1126/science.1097403 2004

    Abstract:

    Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.

  142. Wanninkhof, R.H., and F.J. Millero. Sea keepers network to study sea's role in absorbing greenhouse gases. Showboats International (January issue), 71, 2004

    Abstract:

    No abstract.

  143. Wanninkhof, R.H., and R.A. Feely. Observing the global oceanic carbon cycle, pp. 12-28. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate, D.M. Stanitski (ed.). NOAA Office of Climate Observation, Silver Spring, MD, 307 pp., 2004

    Abstract:

    No abstract.

  144. Wanninkhof, R.H., K.F. Sullivan, and Z. Top. Air-sea gas transfer in the Southern Ocean. Journal of Geophysical Research, 109(C8):C08S19, 12 pp., doi:10.1029/2003JC001767 2004

    Abstract:

    Gas transfer velocities were determined in the Southern Ocean during the Southern Ocean Iron Fertilization experiment (SOFex) using the dual deliberate tracer technique. The decrease of the purposefully injected tracers, sulfur hexafluoride and helium-3, could be well described by gas exchange parameterizations with wind speed that satisfy global constraints based on bomb-14C uptake. The concentration decrease of tracers could be predicted slightly better with established relationships if gas transfer was modeled as a function of the cube rather than the square of the wind speed, particularly over a time interval with high and variable winds. However, both fits can model the concentration decrease within the uncertainty of the observations. This suggests that it will be singularly difficult to definitively determine if a quadratic or cubic dependence of gas exchange with wind is more appropriate based on deliberate tracer measurements. However, these results show that gas exchange rates in the Southern Ocean are not anomalous when compared with the rest of the ocean. Thus, this cannot account for discrepancy between observational and model-based estimates of uptake of CO2 in the Southern Ocean. Using a high-quality wind speed field obtained from the QuikSCAT satellite Seawinds scatterometer and an established surface water pCO2 climatology, the CO2 uptake in the Southern Ocean (>34°S) is reassessed. The total uptake rates are similar to previous observation-based estimates, but the analysis shows that the uptake rate is sensitive to wind speed product used and the wind speed distribution.

  145. Ward, B., R.H. Wanninkhof, P.J. Minnett, and M.J. Head. SkinDeEP: A profiling instrument for upper-decameter sea surface measurements. Journal of Atmospheric and Oceanic Technology, 21(2):207-222, doi:10.1175/1520-0426(2004)021<0207:SAPIFU>2.0.CO; 2004

    Abstract:

    The Skin Depth Experimental Profiler (SkinDeEP) is an autonomous, self-contained, hydrodynamic instrument capable of making repeated, high-resolution profiles of temperature and conductivity within the ocean's upper decameter. Autonomous profiling operation is accomplished through SkinDeEP's ability to change its density: positive buoyancy is achieved by pumping air from inside the body of the profiler into an external, neoprene, inflatable sleeve; the instrument sinks when the sleeve is deflated by returning the air to the interior. The sensors are mounted some distance from the top endcap and data are recorded only during the ascending phase of the profile so as to minimize disruption of a naturally occurring scalar structure by the presence of the instrument. Temperature and conductivity are measured with resolutions in the submillimeter and millimeter ranges, respectively. Highly accurate and slower sensors are installed for calibration purposes. These data are used to study exchange processes at the air-sea interface and the structure of the ocean just below.

  146. Ward, B., R.H. Wanninkhof, W.R. McGillis, A.T. Jessup, M.D. DeGrandpre, J.E. Hare, and J.B. Edson. Biases in the air-sea flux of CO2 resulting from ocean surface temperature gradients. Journal of Geophysical Research, 109(C8):C08S08, 14 pp., doi:10.1029/2003JC001800 2004

    Abstract:

    The difference in the fugacities of CO2 across the diffusive sublayer at the ocean surface is the driving force behind the air-sea flux of CO2. Bulk seawater fugacity is normally measured several meters below the surface, while the fugacity at the water surface, assumed to be in equilibrium with the atmosphere, is measured several meters above the surface. Implied in these measurements is that the fugacity values are the same as those across the diffusive boundary layer. However, temperature gradients exist at the interface due to molecular transfer processes, resulting in a cool surface temperature, known as the skin effect. A warm layer from solar radiation can also result in a heterogeneous temperature profile within the upper few meters of the ocean. Here we describe measurements carried out during a 14-day study in the equatorial Pacific Ocean (GasEx-2001) aimed at estimating the gradients of CO2 near the surface and resulting flux anomalies. The fugacity measurements were corrected for temperature effects using data from the ship's thermosalinograph, a high-resolution profiler (SkinDeEP), an infrared radiometer (CIRIMS), and several point measurements at different depths on various platforms. Results from SkinDeEP show that the largest cool skin and warm layer biases occur at low winds, with maximum biases of -4% and +4%, respectively. Time series ship data show an average CO2 flux cool skin retardation of about 2%. Ship and drifter data show significant CO2 flux enhancement due to the warm layer, with maximums occurring in the afternoon. Temperature measurements were compared to predictions based on available cool skin parameterizations to predict the skin-bulk temperature difference, along with a warm layer model.

  147. Chung, S.-N., K. Lee, R.A. Feely, C.L. Sabine, F.J. Millero, R.H. Wanninkhof, J.L. Bullister, R.M. Key, and T.-H. Peng. Calcium carbonate budget in the Atlantic Ocean based on water column inorganic carbon chemistry. Global Biogeochemical Cycles, 17(4):1093, 16 pp., doi:10.1029/2002GB002001 2003

    Abstract:

    Recent independent lines of evidence suggest that the dissolution of calcium carbonate (CaCO3) particles is substantial in the upper ocean above the calcite 100% saturation horizon. This shallow-water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic CaCO3 at shallow water depths. Here we use more than 20,000 sets of carbon measurements in conjunction with CFC and 14C data from the WOCE/JGOFS/OACES global CO2 survey to estimate in-situ dissolution rates of CaCO3 in the Atlantic Ocean. A dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface. The in-situ CaCO3 dissolution increases rapidly at the aragonite 100% saturation horizon. Estimated dissolution rates north of 40°N are generally higher than the rates to the south, which is partly attributable to the production of exported CaCO3 being higher in the North Atlantic than in the South Atlantic. As more CaCO3 particles move down the water column, more particles are available for in-situ dissolution. The total water column CaCO3 dissolution rate in the Atlantic Ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5.6 x 1012 mol C yr-1 from CaCO3-rich sediments. The resulting water column dissolution rate of CaCO3 for the Atlantic Ocean is approximately 11.1 x 1012 mol C yr-1. This corresponds to about 31% of a recent estimate (35.8 x 1012 mol C yr-1) of net CaCO3 production by Lee (2001) for the same area. Our calculation using a large amount of high-quality water column alkalinity data provides the first basin-scale estimate of the CaCO3 budget for the Atlantic Ocean.

  148. Crusius, J., and R.H. Wanninkhof. Gas transfer velocities measured at low wind speed over a lake. Limnology and Oceanography, 48(3):1010-1017, 2003

    Abstract:

    The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ~3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 < ~3.7 m s-1, with a linear dependence on wind speed at higher wind speeds. The lack of a unique relationship between transfer velocity and wind speed at low wind speeds suggests that other processes, such as convective cooling, contribute significantly to gas exchange when the wind speeds are low. All three proposed relationships clearly show a strong dependence on wind for winds >3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ~3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

  149. Lee, K., S.-D. Choi, G.-H. Park, R.H. Wanninkhof, T.-H. Peng, R.M. Key, C.L. Sabine, R.A. Feely, J.L. Bullister, F.J. Millero, and A. Kozyr. An updated anthropogenic CO2 inventory in the Atlantic Ocean. Global Biogeochemical Cycles, 17(4):1116, 17 pp., doi:10.1029/2003GB002067 2003

    Abstract:

    This paper presents a comprehensive analysis of the basin-wide inventory of anthropogenic CO2 in the Atlantic Ocean based on high-quality inorganic carbon, alkalinity, chlorofluorocarbon, and nutrient data collected during the World Ocean Circulation Experiment (WOCE) Hydrographic Program, the Joint Global Ocean Flux Study (JGOFS), and the Ocean-Atmosphere Carbon Exchange Study (OACES) surveys of the Atlantic Ocean between 1990 and 1998. Anthropogenic CO2 was separated from the large pool of dissolved inorganic carbon using an extended version of the DELTA-C* method originally developed by Gruber et al. (1996). The extension of the method includes the use of an optimum multiparameter analysis to determine the relative contributions from various source water types to the sample on an isopycnal surface. Total inventories of anthropogenic CO2 in the Atlantic Ocean are highest in the subtropical regions at 20°-40°, whereas anthropogenic CO2 penetrates the deepest in high-latitude regions (>40°N). The deeper penetration at high northern latitudes is largely due to the formation of deep water that feeds the Deep Western Boundary Current, which transports anthropogenic CO2 into the interior. In contrast, waters south of 50°S in the Southern Ocean contain little anthropogenic CO2. Analysis of the data collected during the 1990-1998 period yielded a total anthropogenic CO2 inventory of 28.4 ± 4.7 Pg C in the North Atlantic (equator-70°N) and of 18.5 ± 3.9 Pg C in the South Atlantic (equator-70°S). These estimated basin-wide inventories of anthropogenic CO2 are in good agreement with previous estimates obtained by Gruber (1998), after accounting for the difference in observational periods. Our calculation of the anthropogenic CO2 inventory in the Atlantic Ocean, in conjunction with the inventories calculated previously for the Indian Ocean (Sabine et al., 1999) and for the Pacific Ocean (Sabine et al., 2002), yields a global anthropogenic CO2 inventory of 112 ± 17 Pg C that has accumulated in the world oceans during the industrial era. This global oceanic uptake accounts for approximately 29% of the total CO2 emissions from the burning of fossil fuels, land-use changes, and cement production during the past 250 years.

  150. Macdonald, A.M., M.O. Baringer, R. Wanninkhof, K. Lee, and D.W.R. Wallace. A 1998-1992 comparison of inorganic carbon and its transport across 24.5°N in the Atlantic. Deep-Sea Research, Part II, 50(22-26):3041-3064, doi:10.1016/j.dsr2.2003.07.009 2003

    Abstract:

    In January and February 1998, when an unprecedented fourth repetition of the zonal hydrographic transect at 24.5°N in the Atlantic was undertaken, carbon measurements were obtained for the second time in less than a decade. The field of total carbon along this section is compared to that provided by a 1992 cruise which followed a similar path (albeit in a different season). Consistent with the increase in atmospheric carbon levels, an increase in anthropogenic carbon concentrations of 8 ± 3 mol kg-1 was found in the surface layers. Using an inverse analysis to determine estimates of absolute velocity, the flux of inorganic carbon across 24.5° is estimated to be -0.74 ± 0.91 and -1.31 ± 0.99 Pg Cyr-1 southward in 1998 and 1992, respectively. Estimates of total inorganic carbon flux depend strongly upon the estimated mass transport, particularly of the Deep Western Boundary Current. The 1998 estimate reduces the large regional divergence in the meridional carbon transport suggested by previous studies and brings into question the idea that the tropical Atlantic constantly outgasses carbon, while the subpolar Atlantic sequesters it. Uncertainty in the carbon transports themselves, dominated by the uncertainty in the total mass transport estimates, are a hindrance to determining the "true" picture. The flux of anthropogenic carbon (C*ANTH) across the two transects is estimated as northward at 0.20 ± 0.08 and 0.17 ± 0.06 Pg Cyr-1 for the 1998 and 1992 sections, respectively. The net transport of C*ANTH across 24.5°N is strongly affected by the difference in concentrations between the northward flowing shallow Florida Current and the mass balancing, interior return flow. The net northward transport of C*ANTH is opposite the net flow of total carbon and suggests, as has been found by others, that the pre-industrial southward transport of carbon within the Atlantic was stronger than it is today. Combining these flux results with estimates of atmospheric and riverine inorganic carbon input, it is determined that today's oceanic carbon system differs from the pre-industrial system in that today there is an uptake of anthropogenic carbon to the south that is advected northward and stored within the North Atlantic basin.

  151. McGillis, W.R., and R.H. Wanninkhof. SOLAS (Surface Ocean Lower Atmosphere Study) holds first international summer school. U.S. JGOFS Newsletter, 12(3):14-15, 2003

    Abstract:

    No abstract.

  152. Peng, T.-H., R. Wanninkhof, and R.A. Feely. Increase of anthropogenic CO2 in the Pacific Ocean over the last two decades. Deep-Sea Research, Part II, 50(22-26):3065-3082, doi:10.1016/j.dsr.2010.03.008 2003

    Abstract:

    The multiple-parameter linear regression method (Monitoring global ocean carbon inventories, Ocean Observing System Development Panel, Texas A&M University, College Station, TX, 1995, 54 pp; Global Biogeochem. Cycles, 13 (1999) 179) is used to compare inorganic carbon data from the GEOSECS CO2 survey in the Pacific Ocean in 1973 to the WOCE/JGOFS global CO2 survey in the 1990s. A model of total dissolved inorganic carbon (DIC) as a function of five variables (AOU, theta, S, Si, and PO4) has been developed from the recent CO2 survey data (namely CGC91 and CGC96) in the Pacific Ocean. After correcting for a systematic DIC offset of -30.3 ± 7 mol kg-1 from the GEOSECS data, the residual DIC based on this model as computed from GEOSECS data has been used to estimate the anthropogenic CO2 penetration in the Pacific Ocean. In the Northeast Pacific, we obtained an increase of CO2 of 21.3 ± 7.9 mol m-2 over the period from GEOSECS in 1973 to CGC91 in 1991. This gives a mean anthropogenic CO2 uptake rate of 1.3 ± 0.5 mol m-2 yr-1 over this 17 year time period. In the South Pacific, north of 50°S between 180° and 120°W region, the integrated anthropogenic CO2 inventory is estimated to be 19.7 ± 5.7 mol m-2 over the period from GEOSECS in 1974 to CGC96 in 1996. The equivalent mean CO2 uptake rate is estimated to be 0.9 ± 0.3 mol m-2 yr-1 over the 22 years. These results are compared with the isopycnal method (Nature, 396 (1998) 560) to estimate the anthropogenic CO2 signal in the Northeast Pacific (30°N, 152°W) at the crossover region between CGC91 and GEOSECS. The results of the isopycnal method are consistent with those derived from the MLR method. Both methods show an increase in anthropogenic CO2 inventory in the ocean over two decades that is consistent with the increase expected if the ocean uptake has kept pace with the atmospheric CO2 increase.

  153. Wallace, D.W.R., and R.H. Wanninkhof. Ocean-atmosphere exchange and earth-system biogeochemistry. In Marine Science Frontiers for Europe, G. Wefer, F. Lamy, and F. Mantoura (eds.). Springer, Berlin, 107-129, 2003

    Abstract:

    No abstract.

  154. Wanninkhof, R.H., T.-H. Peng, B. Huss, C.L. Sabine, and K. Lee. Comparison of inorganic carbon system parameters measured in the Atlantic Ocean from 1990 to 1998 and recommended adjustments. Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Data Report, ORNL/CDIAC-140, 43 pp., 2003

    Abstract:

    As part of the global synthesis effort sponsored by the Global Carbon Cycle project of the National Oceanic and Atmospheric Administration (NOAA) and U.S. Department of Energy, a comprehensive comparison was performed of inorganic carbon parameters measured on oceanographic surveys carried out under the auspices of the Joint Global Ocean Flux Study and related programs. Many of the cruises were performed as part of the World Hydrographic Program of the World Ocean Circulation Experiment and the NOAA Ocean-Atmosphere Carbon Exchange Study. Total dissolved inorganic carbon (DIC), total alkalinity (TAlk), fugacity of CO2, and pH data from 23 cruises were checked to determine whether there were systematic offsets of these parameters between cruises. The focus was on the DIC and TAlk state variables. Data quality and offsets of DIC and TAlk were determined by using several different techniques. One approach was based on crossover analyses, where the deep-water concentrations of DIC and TAlk were compared for stations on different cruises that were within 100 km of each other. Regional comparisons were also made by using a multiple-parameter linear regression technique in which DIC or TAlk was regressed against hydrographic and nutrient parameters. When offsets of greater than 4 µmol/kg were observed for DIC and/or 6 µmol/kg were observed for TAlk, the data taken on the cruise were closely scrutinized to determine whether the offsets were systematic. Based on these analyses, the DIC data and TAlk data of three cruises were deemed of insufficient quality to be included in the comprehensive basinwide data set. For several of the cruises, small adjustments in TAlk were recommended for consistency with other cruises in the region. After these adjustments were incorporated, the inorganic carbon data from all cruises, along with hydrographic, chlorofluorocarbon, and nutrient data, were combined as a research-quality product for the scientific community.

  155. Asher, W., J. Edson, W.R. McGillis, R.H. Wanninkhof, D.T. Ho, and T. Litchendorf. Fractional area whitecap coverage and air-sea gas transfer velocities measured during GasEx-98. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 199-203, doi:10.1029/GM127p0199 2002

    Abstract:

    GasEx-98 was an air-sea exchange process cruise conducted aboard the NOAA ship Ronald H. Brown in the North Atlantic during May and June of 1998. During the cruise, air-sea gas transfer velocities for carbon dioxide were measured using the direct-covariance method. Because the sampling times for the covariance method are on the same order as the time scales of changes in meteorological forcing, the GasEx-98 results provide a unique data set for investigating whether changes in different forcing mechanisms correlate with changes in gas transfer. In particular, fractional area whitecap coverage, WC, was measured during daylight hours using a dual-camera video system mounted on a bow tower. Several high wind speed events occurred during the cruise, and the resulting correlation between wind speed and WC is consistent with previous oceanic measurements. The whitecap coverage data were combined with the wind speed records and these data were used in a parameterization of whitecap-mediated gas transfer to predict transfer velocities. These predicted transfer velocities are in good agreement with the transfer velocities derived from the direct-covariance data.

  156. Bender, M., S. Doney, R.A. Feely, I. Fung, N. Gruber, D.E. Harrison, R. Keeling, J.K. Moore, J. Sarmiento, E. Sarachik, B. Stephens, T. Takahashi, P. Tans, and R.H. Wanninkhof. A large-scale CO2 observing plan: In situ oceans and atmosphere (LSCOP). NOAA/OAR Special Report (PB2003-100377), 201 pp., 2002

    Abstract:

    This report recommends a strategy for making observations of carbon dioxide (CO2) and related properties in the atmosphere and oceans, over large spatial scales and long timescales. It also recommends process studies of air-sea gas exchange, in order to obtain more accurate estimates of CO2 transfer between the atmosphere and oceans. Models are essential tools for understanding the distributions and fluxes of CO2 in the atmosphere and oceans. We recommend observations and modeling efforts to enhance the skills of models used for this purpose. An ultimate product of the observations, modeling efforts, and complementary process studies will be improved projections of the trajectory of the atmospheric CO2 increase. The report's recommendations are summarized in Table E-1. These recommendations are prepared in the context of the U.S. Carbon Cycle Science Plan (CCSP), with the goal of advancing our ability to address the two fundamental questions that the CCSP posed: (1) what has happened to the carbon dioxide that has already been emitted by human activities (past anthropogenic CO2); and (2) what will be the future atmospheric CO2 concentration trajectory resulting from both past and future emissions? The importance of answering these questions is evident. A recent National Research Council report, Climate Change Science, documents the consensus scientists have reached that human emissions of greenhouse gases are increasingly affecting world climate. The President's speech to the nation on global climate change expressed concern about greenhouse warming at the highest levels of government and committed the United States to confront the issue. These documents recommend conducting the research necessary to understand the environmental behavior of biogenic greenhouse gases, of which carbon dioxide is the most significant. This research will lead toward the knowledge required to accurately project carbon removal rates from the atmosphere to the land biosphere and the oceans. This report presents a plan for large-scale U.S.-sponsored observations of CO2 in the oceans and atmosphere. This plan represents an implementation plan for the CO2 observations component of the CCSP. We recommend observations to track the fate of fossil fuel-derived CO2, to characterize fluxes of CO2 from the atmosphere to the land biosphere and oceans over large scales of space and time, and to achieve process-level understanding of physical and biological controls on those fluxes now and in the future. Complementary small-scale process studies of the land and ocean biospheres are needed for a comprehensive understanding of carbon fluxes and distributions. No specific recommendations for such programs are offered here, because they are being planned independently.

  157. Donelan, M.A., and R.H. Wanninkhof. Gas transfer at water surfaces: Concepts and issues. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 1-10, doi:10.1029/GM127p0001 2002

    Abstract:

    This introductory paper puts the technical articles to follow in the context of the need to understand gas transfer at water surfaces and to apply improved methods to the estimation of the exchange of gases between air and water. We summarize the physical and chemical background to processes of interfacial gas transfer, discuss field and laboratory approaches to measuring the gas exchange rate, and to elucidating its causes. Finally, we illustrate the application of acquired understanding in gas transfer to the global flux of carbon dioxide. This issue is of societal relevance in predicting and possibly reducing anthropogenic causes of climate change.

  158. Donelan, M.A., W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). Gas Transfer at Water Surfaces. AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 383 pp., doi:10.1029/GM127 2002

    Abstract:

    The transfer of gases across the air-water interface has received much attention over the past two decades, particularly in light of increased societal interest in the exchange of greenhouse gases and pollutants between natural water bodies and the atmosphere. Gas transfer at the interface between liquids and gases holds great fascination for a wide range of researchers, from fluid dynamicists to biogeochemists. However, the phenomena of gas transfer, and the problems we face in understanding them, involve daunting issues, including multi-phase flows over a wide range of spatial and temporal scales. Such complexity is increased by the presence of surface films of both natural and anthropogenic origin, which can modify the physical and chemical nature of the interface. As a result, the challenge of working on gas transfer has stimulated the development of multidisciplinary, collaborative efforts and the development of a variety of innovative experimental and observational techniques.

  159. Feely, R.A., J. Boutin, C.E. Cosca, Y. Dandonneau, J. Etcheto, H.Y. Inoue, M. Ishii, C. Le Quere, D.J. Mackey, M. McPhaden, N. Metzl, A. Poisson, and R.H. Wanninkhof. Seasonal and interannual variability of CO2 in the equatorial Pacific. Deep-Sea Research, Part II, 49(13-14):2443-2469, doi:10.1016/S0967-0645(02)00044-9 2002

    Abstract:

    As part of the JGOFS field program, extensive CO2 partial-pressure measurements were made in the atmosphere and in the surface waters of the equatorial Pacific from 1992 to 1999. For the first time, we are able to determine how processes occurring in the western portion of the equatorial Pacific impact the sea-air fluxes of CO2 in the central and eastern regions. These eight years of data are compared with the decade of the 1980s. Over this period, surface-water pCO2 data indicate significant seasonal and interannual variations. The largest decreases in fluxes were associated with the 1991-1994 and 1997-1998 El Niño events. The lower sea-air CO2 fluxes during these two El Niño periods were the result of the combined effects of interconnected large-scale and locally forced physical processes: (1) development of a low-salinity surface cap as part of the formation of the warm pool in the western and central equatorial Pacific; (2) deepening of the thermocline by propagating Kelvin waves in the eastern Pacific; and (3) the weakening of the winds in the eastern half of the basin. These processes serve to reduce pCO2 values in the central and eastern equatorial Pacific towards near-equilibrium values at the height of the warm phase of ENSO. In the western equatorial Pacific there is a small but significant increase in seawater pCO2 during strong El Niño events (i.e., 1982-1983 and 1997-1998) and little or no change during weak El Niño events (1991-1994). The net effect of these interannual variations is a lower-than-normal CO2 flux to the atmosphere from the equatorial Pacific during El Niño. The annual average fluxes indicate that during strong El Niños the release to the atmosphere is 0.2-0.4 Pg Cyr-1 compared to 0.8-1.0 Pg Cyr-1 during non-El Niño years.

  160. Feely, R.A., R.H. Wanninkhof, D.A. Hansell, M.F. Lamb, D. Greeley, and K. Lee. Water column CO2 measurements during the GasEx-98 Expedition. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 173-180, doi:10.1029/GM127p0173 2002

    Abstract:

    During the recent GasEx-98 cruise in the North Atlantic aboard the NOAA ship Ronald H. Brown, carbon measurements were performed in the areas of 46°N, 20.5°W. This process study followed a warm core ring tagged with the deliberately introduced tracer, SF6. Continuous surface water measurements were combined with vertical profiles sampled daily to depths up to 1000 m for carbon mass balance studies. Dissolved inorganic carbon (DIC) and fCO2 measurements were conducted onboard in both underway and discrete analysis modes. During the 25-day experiment in the tagged patch surface water, fCO2 values averaged 275 ± 9 µatm, providing a constant condition of undersaturation and flux of CO2 into the ocean. Using the Wanninkhof (1992) exchange coefficient, the estimated CO2 flux ranged from approximately 1-27 mol m-2 yr-1. The largest CO2 flux occurred during a large wind event beginning on June 6. After the event, DIC and fCO2 values decreased for a few days, as a result of increased productivity associated with the strong mixing event. The DIC results were combined with the TOC, TON, and nutrient data to provide a mass balance for carbon within the patch. The results for the 25-day period indicate DIC increases in the mixed layer ranging from 0.2-1.8 µmol kg-1 d-1 due to gas exchange.

  161. Lamb, M.F., C.L. Sabine, R.A. Feely, R.H. Wanninkhof, R.M. Key, G.C. Johnson, F.J. Millero, K. Lee, T.-H. Peng, A. Kozyr, J.L. Bullister, D. Greeley, R.H. Byrne, D.W. Chipman, A.G. Dickson, C. Goyet, P.R. Guenther, M. Ishii, K.M. Johnson, C.D. Keeling, T. Ono, K. Shitashima, T. Tilbrook, T. Takahashi, D.W.R. Wallace, Y.W. Watanabe, C. Winn, and C.S. Wong. Consistency and synthesis of Pacific Ocean CO2 survey data. Deep-Sea Research, Part II, 49(1-3):21-58, doi:10.1016/S0967-0645(01)00093-5 2002

    Abstract:

    Between 1991 and 1999, carbon measurements were made on 25 WOCE/JGOFS/OACES cruises in the Pacific Ocean. Investigators from 15 different laboratories and four countries analyzed at least two of the four measurable ocean carbon parameters (DIC, TAlk, fCO2, and pH) on almost all cruises. The goal of this work is to assess the quality of the Pacific carbon survey data and to make recommendations for generating a unified data set that is consistent between cruises. Several different lines of evidence were used to examine the consistency, including comparison of calibration techniques, results from certified reference material analyses, precision of at-sea replicate analyses, agreement between shipboard analyses and replicate shore-based analyses, comparison of deep water values at locations where two or more cruises overlapped or crossed, consistency with other hydrographic parameters, and internal consistency with multiple carbon parameter measurements. With the adjustments proposed here, the data can be combined to generate a Pacific Ocean data set, with over 36,000 unique sample locations analyzed for at least two carbon parameters in most cases. The best data coverage was for DIC, which has an estimated overall accuracy of ~3 µmol kg-1. TAlk, the second most common carbon parameter analyzed, had an estimated overall accuracy of ~5 µmol kg-1. To obtain additional details on this study, including detailed crossover plots and information on the availability of the compiled, adjusted data set, visit the Global Data Analysis Project web site at http://cdiac.esd.ornl.gov/oceans/glodap.

  162. Lee, K., D.M. Karl, R. Wanninkhof, and J.-Z. Zhang. Global estimates of net carbon production in the nitrate-depleted tropical and subtropical oceans. Geophysical Research Letters, 29(19):1907, 4 pp., doi:10.1029/2001GL014198 2002

    Abstract:

    Nitrate availability is generally considered to be the limiting factor for oceanic new production and this concept is central in our observational and modeling efforts. However, recent time-series observations off Bermuda and Hawaii indicate a significant removal of total dissolved inorganic carbon (CT) in the absence of measurable nitrate. Here we estimate net carbon production in nitrate-depleted tropical and subtropical waters with temperatures higher than 20°C from the decrease in the salinity normalized CT inventory within the surface mixed layer. This method yields a global value of 0.8 ? 0.3 petagrams of carbon per year (Pg C yr-1, Pg = 1015 grams), which equates to a significant fraction (20-40%) of the recent estimates (20-4.2 Pg C yr-1) of total new production in the tropical and subtropical oceans (Emerson et al., 1997; Lee, 2001). The remainder is presumably supported by upward flux of nutrients into the euphotic zone via eddy diffusion and turbulent mixing processes or lateral exchange. Our calculation provides the first global-scale estimate of net carbon production in the absence of measurable nitrate. We hypothesize that it is attributable to dinitrogen (N2) fixing microorganisms, which can utilize the inexhaustible dissolved N2 pool and thereby bypass nitrate limitation.

  163. Macdonald, A.M., M.O. Baringer, K. Lee, D.W. Wallace, and R.H. Wanninkhof. Subtropical Atlantic carbon transport. International WOCE Newsletter, 42:14-19, 2002

    Abstract:

    No abstract.

  164. Macdonald, A.M., R.H. Wanninkhof, M.O. Baringer, P.E. Robbins, and D.W. Wallace. Oceanic biogeochemical fluxes: A summary of the JGOFS portion of the WOCE/JGOFS Transport Workshop, Southampton, June 25-29, 2001. International WOCE Newsletter, 42:20-21, 2002

    Abstract:

    No abstract.

  165. Millero, F.J., D. Pierrot, K. Lee, R. Wanninkhof, R.A. Feely, C.L. Sabine, R.M. Key, and T. Takahashi. Dissociation constants for carbonic acid determined from field measurements. Deep-Sea Research, Part I, 49(10):1705-1723, doi:10.1016/S0967-0637(02)00093-6 2002

    Abstract:

    A number of workers have recently shown that the thermodynamic constants for the dissociation of carbonic acid in seawater of Mehrbach et al. are more reliable than measurements made on artificial seawater. These studies have largely been confined to looking at the internal consistency of measurements of total alkalinity (TA), total inorganic carbon dioxide (TCO2) and the fugacity of carbon dioxide (fCO2). In this paper, we have examined the field measurements of pH, fCO2, TCO2, and TA on surface and deep waters from the Atlantic, Indian, Southern, and Pacific oceans to determine the pK1, pK2, and pK2-pK1. These calculations are possible due to the high precision and accuracy of the field measurements. The values of pK2 and pK2-pK1 over a wide range of temperatures (-1.6-38°C) are in good agreement (within ±0.005) with the results of Mehrbach et al. The measured values of pK1 at 4°C and 20°C are in reasonable agreement (within ±0.01) with all the constants determined in laboratory studies. These results indicate, as suggested by internal consistency tests, that the directly measured values of pK1+pK2 of Mehrbach et al. on real seawater are more reliable than the values determined for artificial seawater. It also indicates that the large differences of pK2-pK1 (0.05 at 20°C) in real and artificial seawater determined by different investigators are mainly due to differences in pK2. These differences may be related to the interactions of boric acid with the carbonate ion. The values of pK2-pK1 determined from the laboratory measurements of Lee et al. and Lueker et al. at low fCO2 agree with the field-derived data to ±0.016 from 5°C to 25°C. The values of pK2-pK1 decrease as the fCO2 or TCO2 increases. This effect is largely related to changes in the pK2 as a function of fCO2 or TCO2. The values of fCO2 calculated from an input of TA and TCO2, which require reliable values of pK2-pK1, also vary with fCO2. The field data at 20°C has been used to determine the effect of changes of TCO2 on pK2 giving an empirical relationship: pK2TCO2 = pK2-1.6 x 10-4 (TCO2-2050) which is valid at TCO2 > 2050 µmol kg-1. This assumes that the other dissociation constants such as KB for boric acid are not affected by changes in TCO2. The slope is in reasonable agreement with the laboratory studies of Lee et al. and Lueker et al. (-1.2 x 10-4 to -1.9 x 10-4). This equation eliminates the dependence of the calculated fCO2 on the level of fCO2 or TCO2 in ocean waters (σ = 29.7 µatm in fCO2). An input of pH and TCO2 yields values of fCO2 and TA that are in good agreement with the measured values (±22.3 µatm in fCO2 and ±4.3 µmol kg-1 in TA). The cause of the decrease in pK2 at high fCO2 is presently unknown. The observed inconsistencies between the measured and computed fCO2 values may be accounted for by adding the effect of organic acid (~8 µmol kg-1) to the interpretation of the TA. Further studies are needed to elucidate the chemical reactions responsible for this effect.

  166. Soloviev, A., J. Edson, W.R. McGillis, P. Schluessel, and R.H. Wanninkhof. Fine thermohaline structure and gas exchange in the near-surface layer of the ocean during GasEx-98. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 181-185, doi:10.1029/GM127p0181 2002

    Abstract:

    During the GasEx-98 field campaign, observations of the upper ocean structure were performed to identify relationships between the fine thermohaline structure, turbulence, and gas exchange in the near-surface layer of the ocean. The upper ocean dynamics were then simulated using a one-dimensional mixed layer model with the mixing parameterization developed during the TOGA Coupled Ocean-Atmosphere Response Experiment (COARE). The model was initialized with the temperature, salinity, and velocity profiles in the upper 50 m thick layer of the ocean obtained from the conductivity-temperature-depth (CTD) and acoustic Doppler current profiler (ADCP) measurements and was forced with the air-sea heat and momentum fluxes measured by Edson et al. (1999). The model produced a set of parameters, including the time and depth dependent mixing coefficient and the depth of the mixed layer. The simulated mixed layer depth is consistent with the depth of the actively mixed layer determined from the turbulence profiles taken occasionally during GasEx-98 Leg 2 with a free-rising profiler. Moderate wind speed conditions prevailed during GasEx-98 Leg 2 with several storms and a few periods of calm weather. Both the modeling and experimental results demonstrate that under conditions of low wind speed, the surface-generated turbulence is constrained within a relatively thin surface layer of the ocean. In the near-surface layer, appreciable temperature, salinity, and gas concentration differences are formed because of diurnal warming or precipitation effects. These results are applied to the estimation of the effect of mixed layer processes on the bulk-flux formulation for the air-sea exchange of gases.

  167. Takahashi, T., S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, B. Tillbrook, N. Bates, R.H. Wanninkhof, R.A. Feely, C.L. Sabine, J. Olafsson, and Y. Nojiri. Global sea-air CO2 flux based on climatological surface ocean pCO2 and seasonal biological and temperature effects. Deep-Sea Research, Part II, 49(9-10):1601-1622, doi:10.1016/S0967-0645(02)00003-6 2002

    Abstract:

    Based on about 940,000 measurements of surface-water pCO2 obtained since the International Geophysical Year of 1956-1959, the climatological, monthly distribution of pCO2 in the global surface waters representing mean non-El Niño conditions has been obtained with a spatial resolution of 4° × 5° for a reference year 1995. The monthly and annual net sea-air CO2 flux has been computed using the NCEP/NCAR 41-year mean monthly wind speeds. An annual net uptake flux of CO2 by the global oceans has been estimated to be 2.2 (+22% or 19%) Pg Cyr-1 using the (wind speed)2 dependence of the CO2 gas transfer velocity of Wanninkhof (J. Geophys. Res. 97 (1992) 7373). The errors associated with the wind-speed variation have been estimated using one standard deviation (about ±2 m s-1) from the mean monthly wind speed observed over each 4° × 5° pixel area of the global oceans. The new global uptake flux obtained with the Wanninkhof (wind speed)2 dependence is compared with those obtained previously using a smaller number of measurements, about 250,000 and 550,000, respectively, and are found to be consistent within ±0.2 Pg Cyr-1. This estimate for the global ocean uptake flux is consistent with the values of 2.0 ± 0.6 Pg Cyr-1 estimated on the basis of the observed changes in the atmospheric CO2 and oxygen concentrations during the 1990s (Nature 381 (1996) 218; Science 287 (2000) 2467). However, if the (wind speed)3 dependence of Wanninkhof and McGillis (Geophys. Res. Lett. 26 (1999) 1889) is used instead, the annual ocean uptake as well as the sensitivity to wind-speed variability is increased by about 70%. A zone between 40° and 60° latitudes in both the northern and southern hemispheres is found to be a major sink for atmospheric CO2. In these areas, poleward-flowing warm waters meet and mix with the cold subpolar waters rich in nutrients. The pCO2 in the surface water is decreased by the cooling effect on warm waters and by the biological drawdown of pCO2 in subpolar waters. High wind speeds over these low pCO2 waters increase the CO2 uptake rate by the ocean waters. The pCO2 in surface waters of the global oceans varies seasonally over a wide range of about 60% above and below the current atmospheric pCO2 level of about 360 µatm. A global map showing the seasonal amplitude of surface-water pCO2 is presented. The effect of biological utilization of CO2 is differentiated from that of seasonal temperature changes using seasonal temperature data. The seasonal amplitude of surface-water pCO2 in high-latitude waters located poleward of about 40° latitude and in the equatorial zone is dominated by the biology effect, whereas that in the temperate gyre regions is dominated by the temperature effect. These effects are about six months out of phase. Accordingly, along the boundaries between these two regimes, they tend to cancel each other, forming a zone of small pCO2 amplitude. In the oligotrophic waters of the northern and southern temperate gyres, the biology effect is about 35 µatm on average. This is consistent with the biological export flux estimated by Laws et al. (Glob. Biogeochem.Cycles 14 (2000) 1231). Small areas such as the northwestern Arabian Sea and the eastern equatorial Pacific, where seasonal upwelling occurs, exhibit intense seasonal changes in pCO2 due to the biological drawdown of CO2.

  168. Wanninkhof, R.H., S.C. Doney, T. Takahashi, and W.R. McGillis. The effect of using time-averaged winds on regional air-sea CO2 fluxes. In Gas Transfer at Water Surfaces, M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R.H. Wanninkhof (eds.). AGU Geophysical Monograph Series, Volume 127 (ISBN 0-87590-986-8), 351-356, doi:10.1029/GM127p0351 2002

    Abstract:

    Gas transfer velocities are frequently related to wind speeds in order to estimate air-sea gas fluxes on regional and global scales. Since the gas exchange-wind speed relationships are non-linear, the wind speed distribution will have an effect on the fluxes if time-averaged winds are used. Commonly, a Weibull distribution is assumed for monthly or yearly averaged wind speeds. Although this is a reasonable assumption for global winds, significant regional deviations from this distribution exist. For areas with steady winds such as the trade wind regions and Westerlies in the Southern Ocean, the Weibull assumption will overestimate the long-term gas transfer velocities. Using regional wind speed distribution patterns based on 6-hour NCEP re-analysis winds instead of a Weibull distribution, the global oceanic CO2 uptake estimate decreases by 5% if a quadratic dependence with wind speed is assumed and by 26% if a cubic dependence of gas exchange with wind speed is used.

  169. Zhang, J.-Z., G.A. Berberian, and R. Wanninkhof. Long-term storage of natural water samples for dissolved oxygen determination. Water Research, 36(16):4165-4168, doi:10.1016/S0043-1354(02)00093-3 2002

    Abstract:

    A method for preserving natural water samples for dissolved oxygen analysis is recommended. The conventional method of using greased glass stoppers has been found to cause a 12% increase in oxygen concentration over a one-month period as a result of evaporation of water sample through micro-gaps and concurrent intrusion of air into the water sample bottles. Sealing the sample bottles with water has been found to be the optimal storage method. It permits a 100.2 ? 0.3% recovery of dissolved oxygen concentration from storage seawater samples over four months.

  170. Feely, R.A., C.L. Sabine, T. Takahashi, and R. Wanninkhof. Uptake and storage of carbon dioxide in the ocean: The global CO2 survey. Oceanography, 14(4):18-32, doi:10.5670/oceanog.2001.03 2001

    Abstract:

    No abstract.

  171. Fine, R.A., L. Merlivat, W. Roether, P. Schlosser, W.M. Smethie, Jr., and R. Wanninkhof. Observing tracers and the carbon cycle. In Observing the Oceans in the 21st Century: A Strategy for Global Ocean Observations, C.J. Koblinsky and N.R. Smith (eds.). GODAE Project Office and Bureau of Meteorology, Melbourne, Australia, 361-375, 2001

    Abstract:

    No abstract.

  172. Hood, E.M., R.H. Wanninkhof, and L. Merlivat. Short time scale variations of fCO2 in a North Atlantic warm-core eddy: Results from the GASEX-98 carbon interface ocean atmosphere (CARIOCA) buoy data. Journal of Geophysical Research, 106(C2):2561-2572, doi:10.1029/1999JC000278 2001

    Abstract:

    During a Lagrangian deliberate tracer study in the North Atlantic, the 1998 Gas Exchange Experiment (GASEX-98), hourly measurements of wind speed, sea surface temperature, fCO2, and fluorescence were made from two carbon interface ocean atmosphere (CARIOCA) drifting buoys in a warm-core eddy near 46°N and 21.5°W over a period of approximately 20 days. Shipboard measurements of fCO2 near the buoys were used to verify the buoy operation, calibrate the buoy measurements, and assess the performance of the fCO2 sensor. The strong air-sea fCO2 gradient in the eddy and intense atmospheric forcing during the experiment provided ideal conditions for demonstrating the potential of autonomous drift buoy measurements for studies of surface ocean biogeochemistry, where changes of fCO2 were rapid and large. During the experiment, a storm occurred with wind speeds reaching as high as 16-17 m s-1, leading to a sharp decrease in sea surface temperature and an increase in fCO2 of ~30 µatm. The magnitude of this sudden change in fCO2 is equal to approximately half of the annual range of fCO2 in this area. The air-sea flux estimate for the ~20 day experiment using the Wanninkhof (1992) gas transfer velocity formulation was -0.012 mol m-2 d-1 and using the Liss and Merlivat (1986) formulation was -0.007 mol m-2 d-1. The storm event, lasting three to four days, accounted for ~38% of the flux over this period. Approximately 16 hours after the onset of the storm, there was an increase in surface fluorescence coincident with the initial increase in fCO2. Nitrate measurements made from the ship in the eddy show a sharp peak in surface concentrations ~24 hours after the increase in winds and ~6-8 hours after the increase in surface fluorescence. After the upwelling of the NO3 the fluorescence increases more sharply while the fCO2 decreases, consistent with biological productivity. The surface fluorescence measurements remain higher than prestorm conditions for ~5 days after the NO3 has disappeared.

  173. McGillis, W.R., J.B. Edson, J.D. Ware, J.W.H. Dacey, J.E. Hare, C.W. Fairall, and R.H. Wanninkhof. Carbon dioxide flux techniques performed during GasEx-98. Marine Chemistry, 75(4):267-280, doi:10.1016/S0304-4203(01)00042-1 2001

    Abstract:

    A comprehensive study of air-sea interactions focused on improving the quantification of CO2 fluxes and gas transfer velocities was performed within a large open ocean CO2 sink region in the North Atlantic. This study, GasEx-98, included shipboard measurements of direct covariance CO2 fluxes, atmospheric CO2 profiles, atmospheric DMS profiles, water column mass balances of CO2, and measurements of deliberate SF6-3He tracers, along withair-sea momentum, heat, and water vapor fluxes. The large air-sea differences in partial pressure of CO2 caused by a springtime algal bloom provided high signals for accurate CO2 flux measurements. Measurements were performed over a wind speed range of 1-16 m s-1 during the three-week process study. This first comparison between the novel air-side and more conventional water column measurements of air-sea gas transfer show a general agreement between independent air-sea gas flux techniques. These new advances in open ocean air-sea gas flux measurements demonstrate the progress in the ability to quantify air-sea CO2 fluxes on short time scales. This capability will help improve the understanding of processes controlling the air-sea fluxes which, in turn, will improve our ability to make regional and global CO2 flux estimates.

  174. Peltola, E., K. Lee, R.H. Wanninkhof, R. Feely, M. Roberts, D. Greeley, M.O. Baringer, G. Johnson, J. Bullister, C. Mordy, J.-Z. Zhang, P. Quay, F. Millero, D. Hansell, and P. Minnett. Chemical and hydrographic measurements on a Climate and Global Change Cruise along 24°N in the Atlantic Ocean WOCE Section A5R (repeat) during January-February 1998. NOAA Data Report, OAR-AOML-41 (PB2001-107645), 210 pp., 2001

    Abstract:

    This document contains data and metadata from a zonal cruise along nominally 24.5°N in the Atlantic Ocean from Las Palmas, Canary Islands in Spain to Miami, Florida. The cruise took place from January 23 to February 24, 1998 aboard the NOAA Ship Ronald H. Brown under auspices of the National Oceanic and Atmospheric Administration (NOAA). This report presents the analytical and quality control procedures performed during the cruise and bottle data from the cruise. The research was sponsored by the NOAA Climate and Global Change Program under: (i) The Ocean-Atmosphere Carbon Exchange Study (OACES); and (ii) the World Ocean Circulation Experiment (WOCE) repeat hydrography program. Samples were taken from up to 36 depths at 130 stations. The data presented in this report includes the analyses of water samples for: salinity, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity of carbon dioxide (fCO2), total alkalinity (TA), pH, total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), chlorofluorocarbons, and stable carbon isotopic ratio of DIC (13C/12C). Basic hydrographic parameters, pressure, CTD salinity, temperature and the calculated potential temperature, and potential density are included as well.

  175. Wanninkhof, R.H., and P. Liss. SOLAS requirements for the improvement of ocean-atmosphere flux fields. Proceedings, Intercomparison and Validation of Ocean-Atmosphere Flux Fields Workshop, Potomac, MD, May 21-24, 2001. WCRP-115-WMO/TD-No. 1083, 8-9, 2001

    Abstract:

    No abstract.

  176. Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. Enhanced new production observed from the diurnal cycle of nitrate in an oligotrophic anticyclonic eddy. Geophysical Research Letters, 28(8):1579-1582, doi:10.1029/2000GL012065 2001

    Abstract:

    A diurnal study in an anticyclonic eddy provides the first evidence of nutrient dynamics consistent with the observed trends in solar radiation, oxygen concentration changes, and estimates of the eddy diffusive flux of nitrate from nitracline. A new production rate of 24 mmol C m-2 d-1 was determined from nitrate inventory changes at nM levels in the mixed layer using a liquid waveguide technique combined with eddy diffusion estimates across the base of the mixed layer from temporal changes in the vertical penetration of SF6. The new production supported by nitrate from deepening of the mixed layer after storm events is two times larger than that from the daily diffusive flux. Our results demonstrate that new production in the oligotrophic ocean can be enhanced by a supply of nitrate through the eddy turbulence-induced diffusive flux and entrainment during storms.

  177. Lee, K., F.J. Millero, R.H. Byrne, R.A. Feely, and R. Wanninkhof. The recommended dissociation constants for carbonic acid seawater. Geophysical Research Letters, 27(2):229-232, doi:10.1029/1999GL002345 2000

    Abstract:

    A coherent representation of carbonate dissociation constants and measured inorganic carbon species is essential for a wide range of environmentally important issues such as oceanic uptake of anthropogenic CO2 and carbon cycle depictions in ocean circulation models. Previous studies have shown varying degrees of discordance between calculated and measured CO2-system parameters. It is unclear if this is due to errors in thermodynamic models or in measurements. In this work, we address this issue using a large field data set (15,300 water samples) covering all ocean basins. Our field data, obtained using laboratory-calibrated measurement protocols, are most consistent with calculated parameters using the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987). Thus, these constants are recommended for use in the synthesis of the inorganic carbon data collected during the global CO2 survey during the 1990s and for characterization of the carbonate system in seawater.

  178. Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global relationships of total inorganic carbon with temperature and nitrate in surface seawater. Global Biogeochemical Cycles, 14(3):979-994, doi:10.1029/1998GB001087 2000

    Abstract:

    High quality total inorganic carbon (CT) measurements made in the major ocean basins as part of the Joint Global Ocean Flux Study (JGOFS), the National Oceanic and Atmospheric Administration/Ocean Atmosphere Carbon Exchange Study (NOAA/OACES), and the Department of Energy/World Ocean Circulation Experiment (DOE/WOCE) programs are related to sea surface temperature (SST) and nitrate (NO3-).A simple two-parameter function with SST and NO3- of the form NCT = a + b SST + c SST2 + d NO3- fits salinity (S)-normalized surface CT (NCT = CT × 35/S) data for different parts of the oceans within an area-weighted error of ±7 µmol kg-1 (1 sigma). Estimated values of NCT using the derived algorithms with NO3- and SST are compared with values calculated from the surface partial pressure of CO2 (pCO2SW) (Takahashi et al., 1997) and total alkalinity (AT) (Millero et al., 1998) fields using thermodynamic models. Comparisons of the estimated values of NCT with measurements not used to derive the same algorithms, and comparisons with the values calculated from global AT and pCO2SW fields, give a realistic uncertainty of ±15 µmol kg-1 in estimated CT. The derived correlations of NCT with SST and NO3- presented here make it possible to estimate surface CT over the ocean from climatological SST, S, and NO3- fields.

  179. Sabine, C.L., M.F. Lamb, J.L. Bullister, R.A. Feely, G.L. Johnson, R.M. Key, A. Kozyr, K. Lee, F.J. Millero, T.-H. Peng, and R.H. Wanninkhof. U.S. JGOFS team examines Pacific Ocean CO2 data quality. International WOCE Newsletter, 38:10-14, 2000

    Abstract:

    No abstract.

  180. Sabine, C.L., R.H. Wanninkhof, R.M. Key, C. Goyet, and F.J. Millero. Seasonal CO2 fluxes in the tropical and subtropical Indian Ocean. Marine Chemistry, 72(1):33-53, 10.1016/S0304-4203(00)00064-5 doi: 2000

    Abstract:

    Improved estimates of the variability in air-sea CO2 fluxes on seasonal and interannual time scales are necessary to help constrain the net partitioning of CO2 between the atmosphere, oceans, and terrestrial biosphere. Few direct measurements of the carbon system have been made in the main Indian Ocean basin. In the mid 1990s, several global carbon measurement programs focused on the Indian Ocean, greatly increasing the existing carbon database for this basin. This study examines the combined surface CO2 measurements from three major U.S. programs in the Indian Ocean: the global carbon survey cruises, conducted in conjunction with the World Ocean Circulation Experiment (WOCE); the NOAA Ocean-Atmosphere Carbon Exchange Study (OACES) Indian Ocean survey; and the Joint Global Ocean Flux Study (JGOFS) Arabian Sea Process Study. These data are fit with multiparameter linear regressions as a function of commonly-measured hydrographic parameters. These fits are then used with NCEP/NCAR reanalysis and Levitus 94 gridded values to evaluate the seasonal variability of surface seawater CO2 in the tropical and subtropical Indian Ocean and to estimate the magnitude of the Indian Ocean as a net sink for atmospheric CO2. The net annual flux for the Indian Ocean (north of 36°S) was -12.4 ± 0.5 × 1012 mol of carbon (equivalent to -0.15 Pg C) in 1995. The relatively small net flux results from the very different surface water pCO2distributions and seasonal variations in the northern and southern Indian Ocean. The equatorial and northern hemisphere regions have values that are generally above atmospheric values. During the southwest monsoon, pCO2 values in the Arabian Sea coastal upwelling region are among the highest observed in the oceans. The upwelling is seasonal in nature, however, and only affects a relatively small area. The Indian Ocean equatorial region generally has values slightly above atmospheric. Unlike the Pacific and Atlantic Oceans, however, no clear equatorial upwelling signature was observed in 1995. The Southern Hemisphere Indian Ocean, which represents the largest region by area, generally has values below atmospheric. The strongest undersaturations are observed in the austral winter, with summer values reaching near or slightly above atmospheric.

  181. Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. New production in oligotrophic waters: Estimation based on diel cycle of nitrate. Proceedings, Joint Global Ocean Flux Study (JGOFS) Open Science Conference, Bergen, Norway, April 13-17, 2000. JGOFS International Project Office, 76-77, 2000

    Abstract:

    New production can be estimated from accurate measurements of inventory change in nitrate at nM levels in the photic zone. A strong diel cycle was observed in nitrate concentrations in response to photosynthesis in the eastern North Atlantic during the GASEX-98 cruise. During a diel study, nitrate concentration was 92 nM in the morning and decreased to 12 nM by 6 p.m. It increased after dark, presumably due to the diffusive flux from the nitracline. Oxygen showed a similar diel cycle with a change in concentration of about 2 µM. The vertical eddy diffusivity was derived from temporal changes in concentrations of a deliberate tracer, SF6, below the mixed layer. Together with vertical nitrate distributions, the nitrate flux from nitracline throughout the nighttime can account for a nitrate concentration of 102 nM by morning, which is in good agreement with measured nitrate of 92 nM at 6 a.m. The new production estimated from changes of nitrate inventory in the photic zone during the day was 28 mmole C/m2 d. Increases in the mixed layer nitrate were observed during storm events that deepened the mixed layer and brought the nitrate to the surface. The storm-induced nitrate disappeared within two days, indicating a rapid uptake by phytoplankton. The relative importance of sporadic storm events versus daily diffusive flux in supply nitrate to new production can be estimated based on nitrate inventory changes in the photic zone.

  182. Boutin, J., J. Etcheto, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, P.D. Nightingale, N. Metzl, and R.H. Wanninkhof. Satellite sea surface temperature: A powerful tool for interpreting in-situ pCO2 measurements in the equatorial Pacific Ocean. Tellus B, 51(2):490-508, doi:10.1034/j.1600-0889.1999.00025.x 1999

    Abstract:

    In order to determine the seasonal and interannual variability of the CO2 released to the atmosphere from the equatorial Pacific, we have developed pCO2-temperature relationships based upon shipboard oceanic CO2 partial pressure measurements, pCO2, and satellite sea surface temperature, SST, measurements. We interpret the spatial variability in pCO2 with the help of the SST imagery. In the eastern equatorial Pacific, at 5°S, pCO2 variations of up to 100 µatm are caused by undulations in the southern boundary of the equatorial upwelled waters. These undulations appear to be periodic with a phase and a wavelength comparable to tropical instability waves, TIW, observed at the northern boundary of the equatorial upwelling. Once the pCO2 signature of the TIW is removed from the Alize II cruise measurements in January 1991, the equatorial pCO2 data exhibit a diel cycle of about 10 µatm with maximum values occurring at night. In the western equatorial Pacific, the variability in pCO2 is primarily governed by the displacement of the boundary between warm pool waters, where air-sea CO2 fluxes are weak, and equatorial upwelled waters which release high CO2 fluxes to the atmosphere. We detect this boundary using satellite SST maps. East of the warm pool, DELTA-P is related to SST and SST anomalies. The 1985-1997 CO2 flux is computed in a 5° wide latitudinal band as a combination of DELTA-P and CO2 exchange coefficient, K, deduced from satellite wind speed, U. It exhibits up to a factor 2 seasonal variation caused by K-seasonal variation and a large interannual variability, a factor 5 variation between 1987 and 1988. The interannual variability is primarily driven by displacements of the warm pool that makes the surface area of the outgassing region variable. The contribution of DELTA-P to the flux variability is about half of the contribution of K. The mean CO2 flux computed using either the Liss and Merlivat (1986) or the Wanninkhof (1992) K-U parameterization amounts to 0.11 GtC yr-1 or to 0.18 GtC yr-1, respectively. The error in the integrated flux, without taking into account the uncertainly on the K-U parameterization, is less than 31%.

  183. Etcheto, J., J. Boutin, D.C.E. Bakker, Y. Dandonneau, R.A. Feely, H.Y. Inoue, M. Ishii, R.D. Ling, L. Merlivat, P.D. Nightingale, N.Metzl, and R.H. Wanninkhof. pCO2 in the equatorial Pacific and Atlantic Oceans: Determination of air-sea CO2 flux using satellite-borne instruments. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 119-125, 1999

    Abstract:

    No abstract.

  184. Etcheto, J., J. Boutin, Y. Dandonneau, D.C.E. Bakker, R.A. Feely, R.D. Ling, P.D. Nightingale, and R.H. Wanninkhof. Air-sea CO2 flux variability in the equatorial Pacific Ocean near 100°W. Tellus B, 51(3):734-747, doi:10.1034/j.1600-0889.1999.t01-1-00013.x 1999

    Abstract:

    The interannual variability of the CO2 partial pressure(pCO2) in the surface layer of the east equatorial Pacific Ocean near 100°W is studied and compared with the seasurface temperature (SST) monitored from satellites. This variability is shown to be correlated with the SST anomaly rather than with the temperature itself. The pCO2OC variability is related to the variability of the upwelling systems (the equatorial upwelling and the upwelling along the American coast), the main influence being from the coastal upwelling via the surface water advected from the east. A method is derived to interpolate the pCO2OC measurements using the SST satellite measurements. By combining the result with the exchange coefficient (K) deduced from the wind speed provided by satellite-borne instruments, we deduce the air-sea CO2 flux and, for the first time, we continuously monitor its temporal variation. The variability of this flux is mainly due to the variability of K, with a clear seasonal variation. The flux obtained using the Liss and Merlivat (1986) relationship averaged from April 1985 to June 1997 in the region 97.5°-107.5°W, 0-5°S is 1.67 mole m-2 yr-1 of CO2, leaving the ocean with an estimated accuracy of 30%.

  185. Feely, R.A., C.L. Sabine, R.M. Key, T.-H. Peng, and R.H. Wanninkhof. The U.S. global CO2 survey in the North and South Pacific Ocean. Preliminary synthesis results. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 193-198, 1999

    Abstract:

    As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic CO2 uptake in the oceans, the National Oceanic and Atmospheric Administration, the U.S. Department of Energy, and the National Science Foundation have co-sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment (WOCE) and Ocean-Atmospheric Carbon Exchange Study (OACES). The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The new estimates for anthropogenic CO2, employing the Δ-C* method of Gruber et al. (1996), indicate that the largest buildup of anthropogenic CO2 occurs in subtropical waters. Along 155°W, anthropogenic CO2 penetrates to a maximum depth of 900 m at about 37°N in the North Pacific and 1300 m at about 48°S in the South Pacific. Strong shoaling of anthropogenic CO2 occurs southward of 50°S and northward of 48°N. The anthropogenic CO2 inventories from the observations are smaller than the Princeton Ocean Biogeochemical Model (POBM) model estimates, primarily because the Princeton model produces too much deep convective mixing of anthropogenic CO2 in the Southern Ocean.The NCAR Climate System Ocean model, which has very different physics and biological parameterizations, appears to do a better job of reproducing the general patterns in the data-based section.

  186. Feely, R.A., M.F. Lamb, D.J. Greeley, and R.H. Wanninkhof. Comparison of the carbon system parameters at the global CO2 survey crossover locations in the North and South Pacific Ocean between 1990-1996. Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Technical Report, ORNL/CDIAC-115, 73 pp., 1999

    Abstract:

    As a collaborative program to measure global ocean carbon inventories and provide estimates of the anthropogenic carbon dioxide (CO2) uptake by the oceans, the National Oceanic and Atmospheric Administration and the U.S. Department of Energy have sponsored the collection of ocean carbon measurements as part of the World Ocean Circulation Experiment and Ocean-Atmosphere Carbon Exchange Study cruises. The cruises discussed here occurred in the North and South Pacific from 1990 through 1996. The carbon parameters from these 30 crossover locations have been compared to ensure a consistent global data set emerges from the survey cruises. The results indicate that for dissolved inorganic carbon, fugacity of CO2, and pH, the agreement at most crossover locations are well within the design specifications for the global CO2 survey, whereas in the case of total alkalinity, the agreement between crossover locations is not as close.

  187. Feely, R.A., R.H. Wanninkhof, T. Takahashi, and P. Tans. Influence of El Niño on the equatorial Pacific contribution to atmospheric CO2 accumulation. Nature, 398(6728):597-601, doi:10.1038/19273 1999

    Abstract:

    The equatorial ocean is an important CO2 source to the atmosphere, contributing annually 0.7-1.5 Pg of carbon as CO2, as much as 80% of which is attributed to the equatorial Pacific. This source is known to change significantly by ENSO events. To better understand the regional and interannual variability of CO2 fluxes from the equatorial Pacific, field measurements of the partial pressure of CO2 (pCO2) have been made in the equatorial Pacific region since 1992. Here, we report that during the 1991-1994 ENSO period the net annual sea-to-air flux of CO2 was 0.3 PgC from the fall of 1991 to the fall of 1992, 0.6 PgC in 1993, and 0.7 PgC in 1994. These fluxes are 30%-80% of the 0.9 PgC observed during the non-El Niño year of 1996. The total reduction of the sea-to-air CO2 flux during the 1991-1994 El Niño is estimated to be 0.8-1.2 PgC, which accounts for 16-36% of the atmospheric anomaly (the difference between the annual atmospheric CO2 increase in PgC yr-1 and the long-term average increase of 3.18 PgC yr-1) observed over the same period.

  188. Fine, R.A., L. Merlivat, W. Roether, W.M. Smethie, and R.H. Wanninkhof. Observing tracers and the carbon cycle. OCEANOBS99: International Conference on the Ocean Observing System for Climate, Saint Raphael, France, October 18-22, 1999. Centre National d'Etudes Spatiales, Vol. 1,14 pp., 1999

    Abstract:

    A program for repeated sampling of tracers and variables essential for quantitative understanding of the carbon cycle is recommended within CLIVAR/GOOS. The program is critical to our monitoring and understanding of climate change, both natural and anthropogenic. The objectives are: quantification of changes in the rates and spatial patterns of oceanic carbon uptake, fluxes, and storage of anthropogenic CO2; detection and possible quantification of changes in water mass renewal and mixing rates; and provision of a stringent test of the time integration of models' natural and anthropogenic climate variability. The strategy is to put in place a global observing network for tracers and CO2 to document the continuing large-scale evolution of these fields. Hydrographic lines are advocated, although it is realized that there has to be a limit on these observations due to logistical and resource constraints. Thus, there is the need to supplement these observations with time series and autonomous measurements to provide detail in the temporal evolution of the fields.

  189. Lapitan, R.L., R.H. Wanninkhof, and A.R. Mosier. Methods for stable gas flux determination in aquatic and terrestrial systems. In Approaches to Scaling of Trace Gas Fluxes in Ecosystems, A.F. Bouwman (ed.). Elsevier, Amsterdam, 27-66, 1999

    Abstract:

    A general description of the current approaches for measuring trace gas fluxes in aquatic and terrestrial systems is presented in this paper. Our aim is to provide an overview of the current methodologies employed in trace gas flux measurements and the most recent advancements made; with emphasis on the uncertainties observed and potential areas for future developments required to further minimize these uncertainties brought about by spatial and temporal variabilities of fluxes in the field. The increase in sensitivity and improved response time of analytical devices for measuring trace gases within the last five years, such as advancements in laser spectroscopy, have significantly improved the effectiveness of the current methods of measuring these gases in aquatic and terrestrial systems. Systematic errors in trace gas flux estimates have also been reduced with the refinements in estimates of the gas transfer velocity, k, through the use of tracers in the two systems. Footprint corrections of micrometeorological flux measurements in terrestrial systems have provided a better means of identifying the spatial sources of trace gases, and thus, have increased the scope of inference from trace gas flux measurements. Despite these improvements, however, flux measurement errors still remain high. Experimental and sampling designs that can efficiently and effectively deal with the spatial and temporal variabilities in trace gas flux measurements to the minimum are of utmost priority. The same can be said of the modeling procedures; that is, there is a need for an effective method that can reduce instead of propagate potential errors in scaling from field plot to regional or global scales.

  190. Lee, K., R.H. Wanninkhof, R.A. Feely, F.J. Millero, and T.-H. Peng. Global distribution of total inorganic carbon in surface water. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 493-496, 1999

    Abstract:

    No abstract.

  191. Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Interannual variations in oceanic uptake of anthropogenic carbon dioxide for the period of 1982-1995. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 31-34, 1999

    Abstract:

    No abstract.

  192. McGillis, W., J. Edson, and R.H. Wanninkhof. Direct air-sea flux measurements of carbon dioxide over the North Atlantic Ocean and the comparison to indirect methods. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 367-377, 1999

    Abstract:

    To date, large uncertainties in the extent of the CO2 flux between the atmosphere and ocean have prevented us from accurately quantifying how the increasing atmospheric CO2 burden partitions between the ocean and the terrestrial biosphere. This limits our ability to accurately predict future atmospheric CO2 levels. We have recently designed a direct CO2 flux measurement system that considerably improves our estimates of air-sea gas exchange. The system measures the direct air-sea flux of CO2 in the atmospheric boundary layer using eddy correlation (direct covariance). It was successfully deployed during the large scale experiment to study air-sea gas fixes, GASES98, which was conducted in the CO2 sink region of the North Atlantic during May/June of 1998. The seasonal algal bloom caused air-sea pCO2 differences of between -80 to ~100 µatm. This large concentration gradient generated large signals for accurate measurement of the CO2 flux using a close path CO2 sensor. In addition to the CO2 gas flux, the comprehensive atmospheric flux measurement suite included momentum, heat, and moisture fluxes. Atmospheric flux and air-sea gas concentration measurements were performed for over 500 hours, providing more than 1000 observations. Wind speeds between 1 and 16 m/s were experienced over the range of these observations. Preliminary flux estimates from our system compare extremely well with previous estimates of the gas transfer velocity for wind speeds below 7 m/s. At higher wind speeds, the transfer velocities obtained from our system are as much as 20-50% higher than those estimated by empirical relationships. Based on accurate air-sea CO2 coefficients obtained by our investigation and atmospheric and surface ocean pCO2 data obtained to date, estimates of the global ocean CO2 sink are now feasible. Our findings will also provide better predictions of the seasonal and interannual variability of sea-air CO2 flux observed in various global regions.

  193. Peng, T.-H., J.-J. Hung, R.H. Wanninkhof, and F.J. Millero. Carbon budget in the East China Sea in spring. Tellus B, 51(2):531-540, doi:10.1034/j.1600-0889.1999.00028.x 1999

    Abstract:

    Results of total dissolved inorganic carbon (DIC) and total alkalinity (TA) measurements made in the East China Sea (ECS) during a geochemical expedition of KEEP (Kuroshio Edge Exchange Processes) program in May of 1996 show that ECS is a CO2 sink during the spring season. The mean difference of fCO2 (fugacity of CO2) between the atmosphere and surface water is calculated to be 28 µatm, and the resulting net CO2 invasion flux is 2.1 mol/m2/yr, which gives about 0.03 GtC/yr of CO2 uptake in this continental shelf in spring. This study supports the notion that shelf regions can be a significant CO2 sink. The riverine alkalinity, which discharges into ECS, is estimated to be 1,743 µmol/kg on the basis of a linear relationship between TA and salinity. The observed salinity-normalized alkalinity in ECS is higher than that in the open sea, and this excess alkalinity is estimated to be 42 µmol/kg. With the known rate of the Changjiang discharge, this excess TA gives a mean residence time of 1.2 years for the continental shelf water in the ECS. The DIC in the ECS is also found to be higher than that in the open sea. This excess DIC is estimated to be about 76 ± 70 µmol/kg, which is equal to a net carbon input to ECS of 3.9 ± 3.6 mol/m2/yr. Based on the riverine alkalinity input, the equivalent riverine carbon flux from Changjiang discharge is estimated to be about 1.8 mol/m2/yr. With a net CO2 invasion flux of 2.1 ± 2.8 mol/m2/yr, the remaining 0 ± 4.6 mol/m2/yr could come from remineralization of organic matter derived from the biological pump in the shelf or terrestrial sources. Although this preliminary carbon budget implies that gas exchange and riverine input are the main sources of excess carbon in ECS, the contribution of biological carbon flux can not be ruled out because of the large uncertainty associated with these estimates.

  194. Takahashi, T., R.H. Wanninkhof, R.A. Feely, R.F. Weiss, D.W. Chipman, N. Bates, J. Olafsson, C. Sabine, and S.C. Sutherland. Net sea-air CO2 flux over the global oceans: An improved estimate based on the sea-air pCO2 difference. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 9-15, 1999

    Abstract:

    No abstract.

  195. Wanninkhof, R.H. Recent advances in determining air-sea CO2 fluxes. Proceedings, Second International Symposium on CO2 in the Oceans, Tsukuba, Japan, January 18-22, 1999. Center for Global Environmental Research (CGER-I037-99), 101-104, 1999

    Abstract:

    Uncertainties in inverse calculations to determine regional carbon fluxes between the atmospheric, oceanic, and terrestrial reservoirs (Fan et al., 1998) have clearly indicated the need to improve our oceanic carbon flux estimate. There have been significant advances in several aspects of air-sea flux determinations to address this question, including direct estimates of fluxes by co-variance and gradient measurements in the air-boundary layer, extrapolation routines using remote sensing products, and a rapidly increasing observational database of air-sea partial pressure differences. The gas fluxes are commonly expressed as F = k s Δ-pCO2 where F is the air-sea flux CO2 (mol m-2 day-1), k is the gas transfer velocity (m day-1), s is the solubility (mol m3 µatm-1), and Δ-pCO2 is th eair-water partial pressure difference (µatm). This overview discusses recent research aimed at improving estimates of F, k, and Δ-pCO2.

  196. Wanninkhof, R.H., and W.M. McGillis. A cubic relationship between air-sea CO2 and wind speed. Geophysical Research Letters, 26(13):1889-1892, doi:10.1029/1999GL900363 1999

    Abstract:

    Using recent laboratory and field results we explore the possibility of a cubic relationship between gas exchange and instantaneous (or short-term) wind speed, and its impact on global air-sea fluxes. The theoretical foundation for such a dependency is based on retardation of gas transfer at low to intermediate winds by surfactants, which are ubiquitous in the world's oceans, and bubble-enhanced transfer at higher winds. The proposed cubic relationship shows a weaker dependence of gas transfer at low wind speed and a significantly stronger dependence at high wind speed than previous relationships. A long-term relationship derived from such a dependence, combined with the monthly CO2 climatology of Takahashi (1997), leads to an increase in the global annual oceanic CO2 uptake from 1.4 Gigaton C yr-1 to 2.2 Gigaton C yr-1. Although a cubic relationship fits within global bomb-14C oceanic uptake constraints, additional checks are warranted, particularly at high wind speeds where the enhancement is most pronounced.

  197. Wanninkhof, R.H., E. Lewis, R.A. Feely, and F.J. Millero. The optimal carbonate dissociation constants for determining pCO2 from alkalinity and total inorganic carbon. Marine Chemistry, 65(3-4):291-301, doi:10.1016/S0304-4203(99)00021-3 1999

    Abstract:

    In many numerical ocean chemistry models total dissolved inorganic carbon (DIC) and total alkalinity (TA) are transported between subsurface boxes, and partial pressure pCO2 is calculated from TA and DIC in the surface box in order to account for air-sea exchange of carbon dioxide. The conversion is commonly performed by solving the thermodynamic relationships for equilibria between carbonate, bicarbonate, and aqueous CO2 using apparent carbonate dissociation constants. Four independent determinations of the constants have been performed for seawater in the past 50 years. These results have been corrected, refit, and combined by others, creating a virtual cottage industry of laboratory and field verification and cross checks. Here we show that, based on extensive field observations in three major ocean basins, the calculated surface pCO2 from TA and DIC corresponds best with the measured pCO2 of the constants proposed by Mehrbach et al.

  198. Wanninkhof, R.H., S. Doney, T.-H. Peng, J.L. Bullister, K. Lee, and R.A. Feely. Comparison of methods to determine the anthropogenic CO2 invasion into the Atlantic Ocean. Tellus B, 51(2):511-530, doi:10.1034/j.1600-0889.1999.00027.x 1999

    Abstract:

    A comparison of different methods of estimating anthropogenic CO2 into the Atlantic Ocean through the center of the basin between 62°N and 42°S is performed using referenced high quality total dissolved inorganic carbon (DIC) data. The specific anthropogenic input is determined utilizing analytical procedures as described in Gruber et al. (1996), and Chen and Millero (1979) to correct for remineralization and to estimate preanthropogenic endmembers. These estimates are compared with results of the Princeton ocean biogeochemical model (OBM). The results show the specific inventories of anthropogenic carbon agreeing to within 20% but with different uptake patterns. The differences are largely caused by differing assumptions about mixing and winter outcrop endmembers. The same photosynthetic quotients (Redfield ratios) were used each methods. Varying these constants within the range of literature values causes changes in specific inventories of similar magnitude as the different methodologies. Comparison of anthropogenic CO2 uptake and chlorofluorocarbon ages, and preanthropogenic photosynthetic quotients utilizing the analytical methods suggest that anthropogenic CO2 penetration is too shallow following the procedure according to Gruber et al. (1996), and too deep using those of Chen and Millero (1979) in the North Atlantic. The results support previous observations that the uptake of CO2 in the North Atlantic is disproportionate to its surface area. This is caused by a combination of deep water formation and deep winter mixed layers.

  199. Asher, W.E., and R.H. Wanninkhof. The effect of bubble-mediated gas transfer on purposeful dual gaseous-tracer experiments. Journal of Geophysical Research, 103(C5):10,555-10,560, doi:10.1029/98JC00245 1998

    Abstract:

    For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the estimation of transfer velocities for other gases from the transfer velocity calculated using the dual-tracer data. Herein, a method for incorporating the effects of bubble-mediated gas transfer processes on the transfer velocity is presented. This new procedure is used to analyze the data from two recent dual-tracer gas transfer experiments. Transfer velocities that include the effect of bubbles are calculated using the data from two previous oceanic dual-gaseous tracer experiments. Comparing these transfer velocities with transfer velocities calculated by neglecting the effect of bubbles shows that bubble-mediated transfer increased the transfer velocity of helium 3 by 5% at a wind speed of 10.6 m s-1. However, when using the transfer velocities form helium 3 to calculate transfer velocities for carbon dioxide under the same conditions, including the effect of bubbles, decreases the transfer velocity of carbon dioxide by 18%. This shows that bubble-mediated transfer does not have a large effect on the analysis of dual-tracer data, but it is important in relating transfer velocities determined using helium 3 and sulfur hexafluoride to transfer velocities of more soluble gases at wind speeds above 10 m s-1.

  200. Asher, W.E., and R.H. Wanninkhof. Transient tracers and air-sea gas transfer. Journal of Geophysical Research, 103(C8):15,939-15,958, doi:10.1029/98JC00379 1998

    Abstract:

    This paper provides a review of the physics and chemistry associated with air-sea gas transfer of transient atmospheric trace gases and the available laboratory and field measurement techniques used to study air-water gas transfer. The mechanistic principals and their relation to the measurement techniques are used to show that the error associated with estimating air-sea transfer velocities of transient tracers from transfer velocities measured using proxy tracers can be significant if an incorrect dependence of the transfer velocity on molecular diffusivity is assumed. Bubble-mediated transfer processes are also demonstrated to have a significant effect on the parameterization of the transfer velocity.

  201. Castle, R.D., R.H. Wanninkhof, J.L. Bullister, S.C. Doney, R.A. Feely, B.E. Huss, E. Johns, F.J. Millero, K. Lee, D. Frazel, D. Wisegarver, D.Greeley, F. Menzia, M. Lamb, G. Berberian, and L.D. Moore. Chemical and hydrographic profiles and underway measurements from the eastern North Atlantic during July and August of 1993. NOAA Data Report, ERL-AOML-32 (PB98-131865), 82 pp., 1998

    Abstract:

    From July 4-August 30, 1993, the National Oceanic and Atmospheric Administration's (NOAA) Ocean-Atmosphere Carbon Exchange Study (OACES) and Radiatively Important Trace Species (RITS) programs participated in an oceanographic research cruise aboard the NOAA ship Malcolm Baldrige. The objectives of the OACES component were to determine the source and sink regions of CO2 in the equatorial and North Atlantic during the summer and to establish a baseline of total carbon inventory in the region. Data were collected from 5°S to Iceland along a nominal longitude of 20°W. This report presents only the OACES-related data from legs 1, 2A, and 2B, including hydrography, nutrients, carbon species, dissolved oxygen, total inorganic carbon, chlorofluorocarbons, total alkalinity, pH, and salinity. Included are contour plots of the various parameters and descriptions of the sampling techniques and analytical methods used in data collection.

  202. Doney, S.C., J.L. Bullister, and R.H. Wanninkhof. Climatic variability in upper ocean ventilation rates diagnosed using chlorofluorocarbons. Geophysical Research Letters, 25(9):1399-1402, doi:10.1029/98GL00844 1998

    Abstract:

    The chlorofluorocarbon CFC-12 (CCl2-F2) distributions from two occupations of a meridional hydrographic section in the eastern North Atlantic are used to describe the oceanic penetration of CFCs and change in the integrated ventilation patterns over the five years from 1988 to 1993. The CFC-12 water-column inventories increased by 30-40%, despite a slowing atmospheric growth rate (14%), because of continuing uptake by undersaturated subsurface water masses whose response is lagged by the ventilation time-scales. After removing the long-term CFC temporal trend using a tracer age based normalization technique, we observe a distinct dipole pattern in upper ocean ventilation, with reduced convection in the subpolar gyre and enhanced production of saline subtropical underwater in 1993. These differences are discussed in relation to interannual variability in atmospheric surface forcing, upper ocean anomalies, and convection patterns associated with the North Atlantic Oscillation.

  203. Feely, R.A., R.H. Wanninkhof, H.B. Milburn, C.E. Cosca, M. Stapp, and P.P. Murphy. A new automated underway system for making high precision pCO2 measurements onboard research ships. Analytica Chimica Acta, 377(2-3):185-191, doi:10.1016/S0003-2670(98)00388-2 1998

    Abstract:

    We have developed a new temperature-controlled, automated underway system for making atmospheric and surface ocean pCO2 measurements onboard research vessels equipped with an uncontaminated seawater intake system. Uncontaminated seawater is supplied to a showerhead plexiglass equilibrator at the rate of approximately 50 liters/minute. After about 3 minutes, the air trapped in the equilibrator is equilibrated with seawater. This air is sampled six times per hour. In addition, atmospheric air is sampled three times per hour from the intake on the bow flagstaff through 3/8" DekabonTM tubing to the underway system. The CO2 measurements are made with a differential, non-dispersive, infrared analyzer LiCorTM (model 6252). The underway system operates on an hourly cycle with the first quarter of each hour devoted to calibration with three CO2 standards, each measured for 5 minutes. A second order polynomial calibration curve is calculated from the voltage values of the standards. The remaining time in each hour is used to measure equilibrator air (15 min), bow air (15 min), and equilibrator air once again (15 min). To date, we have successfully used the underway pCO2 system on 12 cruises of the NOAA Ship Ka'imimoana in the equatorial Pacific. The analytical precision of the system is approximately 0.3-0.4 ppm for seawater and for air.

  204. Lee, K., R.H. Wanninkhof, T. Takahashi, S.C. Doney, and R.A. Feely. Low interannual variability in recent oceanic uptake of atmospheric carbon dioxide. Nature, 396(6707):155-158, doi:10.1038/24139 1998

    Abstract:

    An improved understanding of the partitioning of carbon between the atmosphere, terrestrial biosphere, and ocean allows for more accurate predictions of future atmospheric CO2 concentrations under various fossil-fuel CO2 emission scenarios. One of the more poorly quantified relevant processes is the interannual variability in the uptake of fossil-fuel CO2 from the atmosphere by the terrestrial biosphere and ocean. Existing estimates, based on atmospheric measurements, indicate that the oceanic variability is large. Here we estimate the interannual variability in global net air-sea CO2 flux using changes in the observed wind speeds and the partial pressure of CO2 (pCO2) in surface seawater and the overlying air. Changes in seawater pCO2 are deduced from interannual anomalies in sea surface temperature and the regionally and seasonally varying temperature-dependence of seawater pCO2, assuming that variations in sea surface temperature reflect seawater pCO2 changes caused by thermodynamics, biological processes, and water mixing. The calculated interannual variability in oceanic CO2 uptake of 0.4 Gt C yr-1(2 sigma) is much less than that inferred from the analysis of atmospheric measurements. Our results suggest that variable sequestration of carbon by the terrestrial biosphere is the main cause of observed year-to-year variations in the rate of atmospheric CO2 accumulation.

  205. McElligott, S., R.H. Byrne, K. Lee, R.H. Wanninkhof, F.J. Millero, and R.A. Feely. Discrete water column measurements of CO2 fugacity and pHT in seawater: A comparison of direct measurements and thermodynamic calculations. Marine Chemistry, 60(1-2):63-73, doi:10.1016/S0304-4203(97)00080-7 1998

    Abstract:

    The NOAA Equatorial Pacific CO2 system data set (~2500 water samples) has been evaluated to assess the internal consistency of measurements and calculations involving CO2 fugacity and pHT. This assessment represents the first large scale field comparison of pHT and fCO2 data. Comparisons of direct discrete CO2 fugacity (fCO2) measurements with CO2 fugacity calculated from total inorganic carbon (CT), total alkalinity (AT), and spectrophotometric pH (pHT = -log[H+]T) indicate that a variety of improvements are needed in the parameter measurements and thermodynamic relationships used to relate fCO2, CT, AT, and pHT in seawater. CO2 fugacity calculated from CT and pHT or AT and pHT agree with direct measurements to no better than 1%. Comparisons of measured fugacity, fCO2 (measured), and CO2 fugacity calculated from CT and pHT, fCO2 (CT, pHT), indicate that the precision of fCO2 calculations is good relative to direct measurements. In contrast, due to the extreme sensitivity of fCO2 and [H+]T calculations to relatively small errors in both CT and AT, CO2 fugacity, as well as [H+]T, calculated from CT and AT are very imprecise and render comparisons with direct measurements of little use. Consequently, precise calculations of fCO2 require the use of direct pHT measurements.

  206. Murphy, P.P., R.A. Feely, and R.H. Wanninkhof. On obtaining high-precision measurements of oceanic pCO2 using infrared analyzers. Marine Chemistry, 62(1-2):103-115, doi:10.1016/S0304-4203(98)00030-9 1998

    Abstract:

    Assessments of ocean carbon uptake using the air-sea disequilibrium of CO2 require very high quality measurements of pCO2 in the atmosphere and in surface seawater. These measurements are often collected and analyzed using infrared detectors. Laboratory data are presented here which suggest that errors of the order of several parts per million in xCO2 can result if the analyzer temperature and pressure are not carefully matched during calibration and sampling. Field data were examined to address questions about the importance of measuring analysis temperature and pressure under more extreme conditions, sample averaging, and calibration frequency. The results indicate that calibration frequency can be minimized without significant compromises in data quality if the analyzer temperatures and pressures are suitably monitored and/or controlled. Daily calibrations gave results to within 0.4 ppm of the results obtained by hourly calibration when the temperature of the analyzer was controlled to ±0.2°C and the voltages were corrected for pressure differences between calibration and sampling.

  207. Peltola, E., R. Wanninkhof, R. Molinari, B.E. Huss, R. Feely, J. Bullister, J.-Z. Zhang, F. Chavez, A. Dickson, A. Ffield, D. Hansell, F. Millero, P. Quay, R. Castle, G. Thomas, R. Roddy, T. Landry, M. Roberts, H. Chen, D. Greeley, K. Lee, M. Roche, J.A. Goen, F. Millero, K. Buck, M. Kelly, F. Menzia, A. Huston, T. Waterhouse, S. Becker, and C. Mordy. Chemical and hydrographic measurements during the Indian Ocean I8 repeat cruise (IR8N) in September and October 1995. NOAA Data Report, ERL-AOML-34 (PB99-126948), 176 pp., 1998

    Abstract:

    This document contains data and metadata from the I8 repeat cruise in the Indian Ocean cruise in 1995 from Fremantle, Australia to Male in the Maldives. From September 22 to October 25, 1995, the National Oceanic and Atmospheric Administration (NOAA) sponsored an oceanographic research cruise conducted aboard the NOAA Ship Malcolm Baldrige. This report presents the analytical and quality control procedures and data from the cruise that was conducted for the Ocean-Atmosphere Carbon Exchange Study (OACES). Samples were taken at 101 stations. The data presented in this report includes hydrography, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity of carbon dioxide (fCO2), total alkalinity (TA), pH, total organic carbon and nitrogen data (TOC/TON), chlorofluorocarbons, 13C, and biological parameters.

  208. Peng, T.-H., R.H. Wanninkhof, J.L. Bullister, R.A. Feely, and T. Takahashi. Quantification of decadal anthropogenic CO2 uptake in the Indian Ocean based on dissolved inorganic carbon measurements. Nature, 396(6711):560-563, doi:10.1038/25103 1998

    Abstract:

    The increase of total dissolved inorganic carbon (DIC) in the ocean caused by the uptake of fossil fuel CO2 is estimated mostly by ocean models. These model estimates need to be verified using field measurements. However, the direct detection of the anthropogenic CO2 signal in the ocean has been hampered by the relatively small annual increase in DIC in seawater (~1 µmol/kg/yr, as compared with background DIC of ~2000 µmol/kg) and by lack of high-precision measurements in the past. With the recent improvement in DIC analyses techniques, it has now become possible to detect the anthropogenic CO2 signal on decadal time scales. Here we report a significant increase in DIC between the GEOSECS survey in 1978 and the recent NOAA-OACES survey in 1995 in the Indian Ocean. The anthropogenic CO2 signal is 12 ± 4.5 µmol/kg at ~300 m (potential density, σθ = 26.6) and the signal decreases on denser isopycnal horizons down to undetectable near ~1000 m (σθ = 27.2). The data are used to illustrate the isopycnal analysis and corrections necessary to determine the anthropogenic CO2 increase over time. The work can be used as a guide for future observational strategies to assess uptake of anthropogenic CO2.

  209. Wanninkhof, R.H., and R.A. Feely. fCO2 dynamics in the Atlantic, Pacific, and South Indian Oceans. Marine Chemistry, 60(1-2):15-31, doi:10.1016/S0304-4203(97)00088-1 1998

    Abstract:

    Subsurface fugacities of CO2 (fCO2(20)) can be used in combination with total dissolved inorganic carbon (DIC) to precisely calculate total alkalinity. Thus, it can be used to determine dissolution of calcium carbonate (hard tissue) and remineralization of organic material (soft tissue), to quantify saturation constants of calcite and aragonite in seawater, and to characterize water masses. fCO2(20) is a good tracer of biological transformation since it is thermodynamically related to the other inorganic carbon system parameters and it has a dynamic range from 200 to 2000 µatm in the world's ocean. Precision of fCO2 measurements is better than 0.3% and the values are well calibrated using compressed gas reference standards. Increases of fCO2(20) are observed as the water masses age during movement from the Atlantic to the Indian and South Pacific Oceans. As an example of the determination of the ratio of soft tissue remineralization to hard tissue dissolution from fCO2(20) and DIC, the trends along the 27.2 isopyncal for the subtropical gyres of the three basins are investigated. Little CaCO3 dissolves along this isopycnal in the Atlantic and the South Pacific while the soft tissue remineralization to hard tissue dissolution ratio in the Indian Ocean is 4.5:1. The difference in this ratio along the 27.2 isopycnal appears to be a combination of the calcite and aragonite saturation levels and the supply of aragonite tests.

  210. Feely, R.A., R.H. Wanninkhof, C. Goyet, D.E. Archer, and T. Takahashi. Variability of CO2 distributions and sea-air fluxes in the central and eastern equatorial Pacific during the 1991-1994 El Niño. Deep-Sea Research, Part II, 44(9-10):1851-1867, doi:10.1016/S0967-0645(97)00061-1 1997

    Abstract:

    As part of the U.S. JGOFS Program and the NOAA Ocean-Atmosphere Carbon Exchange Study (OACES), measurements of CO2 partial pressure were made in the atmosphere and in the surface waters of the central and eastern equatorial Pacific during the boreal spring and autumn of 1992, the spring of 1993, and the spring and autumn of 1994. Surface-water pCO2 data indicate significant diurnal, seasonal, and interannual variations. The largest variations were associated with the 1991-1994 ENSO event, which reached maximum intensity in the spring of 1992. The lower values of surface-water DELTApCO2 observed during the 1991-1994 ENSO period were the result of the combined effects of both remotely and locally forced physical processes. The warm pool, which reached a maximum eastward extent in January-February of 1992, began in September of 1991 as a series of westerly wind events lasting about 30 days. Each wind event initiated an eastward-propagating Kelvin wave which caused a deepening of the thermocline. By the end of January 1992 the thermocline was at its maximum depth, so that the upwelled water was warm and CO2-depleted. In April of the same year, the local winds were weaker than normal, and the upwelling was from shallow depths. These changes resulted in a lower-than-normal CO2 flux to the atmosphere. The results show that for the one-year period from the fall of 1991 until the fall of 1992, approximately 0.3 GtC were released to the atmosphere; 0.6 GtC were released in 1993, and 0.7 GtC in 1994, in good agreement with the model results of Ciais et al. (Science, 269, 1098-1102; J. Geophys. Res., 100, 5051-5070). The net reduction of the ocean-atmosphere CO2 flux during the 1991-1994 El Niño was on the order of 0.8-1.2 GtC. Thus, the total amount of CO2 sequestered in the equatorial oceans during the prolonged 1991-1994 El Niño period was about 25% higher than the severe El Niño of 1982-1983.

  211. Ho, D.T., L.F. Bliven, R.H. Wanninkhof, and P. Schlosser. The effect of rain on air-water gas exchange. Tellus B, 49(2):149-158, doi:10.1034/j.1600-0889.49.issue2.3.x 1997

    Abstract:

    The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain- Sea Interaction Facility (RSIF) using several SF6 evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with 18 different rain rates (7 to 110 mm h-1) and 1 of 2 dropsizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and dropsize. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

  212. Ho, D.T., R.H. Wanninkhof, J.C. Masters, R.A. Feely, and C.E. Cosca. Measurement of underway fCO2 in the eastern equatorial Pacific on NOAA Ships Malcolm Baldrige and Discoverer from February to September 1994. NOAA Data Report, ERL-AOML-30 (PB97-169056), 66 pp., 1997

    Abstract:

    From February through September 1994, underway measurements of the fugacity (partial pressure) of carbon dioxide (fCO2) were performed in the eastern equatorial Pacific as part of the Ocean Atmosphere Carbon Exchange Study (OACES) of the National Oceanic and Atmospheric Administration (NOAA). The measurements were performed with semi-autonomous instruments which measured the fugacity in the air and in the headspace of an equilibrator drawing water from the bow of the ship, from which the fCO2 of the surface water is calculated. From the difference in fugacity in air and water, the CO2 flux from the equatorial Pacific can be estimated. On the NOAA Ship Malcolm Baldrige the system measured three reference standards, three air values, and eight water values per hour. The system on the Discoverer measured three standards, one 19-minute average air sample, and one 20-minute average water sample per hour. This report contains a description of the methodology and reduction of the fCO2 and ancillary measurements. The results from the cruises of the Malcolm Baldrige in the equatorial Pacific in the (boreal) spring and fall of 1994 and from the Discoverer along nominally 110°W in the spring of 1994 are shown in a series of graphs with fCO2 air and water versus latitude as top panel and temperature and salinity versus latitude as bottom panel.

  213. Lamb, M.F., J.L. Bullister, R.A. Feely, G.C. Johnson, D.P. Wisegarver, B. Taft, R.H. Wanninkhof, K.E. McTaggart, K.A. Krogslund, C.W. Mordy, K. Hargreaves, D. Greeley, T. Lantry, H. Chen, B.E. Huss, F.J. Millero, R.H. Byrne, D.A. Hansell, F.P. Chavez, P.D. Quay, P.R. Guenther, J.-Z.Zhang, W. Gardner, M.J. Richardson, and T.-H. Peng. Chemical and hydrograph measurements in the eastern Pacific during the CGC94 expedition (WOCE section P18). NOAA Data Report, ERL-PMEL-61 (PB97-158075), 235 pp., 1997

    Abstract:

    NOAA's Climate and Global Change (CGC) Program sponsored a major cooperative effort in the eastern Pacific along WOCE Hydrographic Programme Line P18 from 26 January to 27 April 1994. The first leg (Leg 1) consisted of a transit from Seattle to Punta Arenas, Chile. The second leg (Leg 2) covered hydrographic stations from 67°S, 103°W to 27°S, 103°. The third leg (Leg 3) included stations between 26.5°S, 103°W and 23°N, 110°W. Full depth CTD/rosette casts were made to the ocean bottom at a nominal spacing of 30 miles on Legs 2 and 3. Water samples were collected on the casts for analyses of concentrations of salinity, DO, CFC, fCO2, DIC, TAlk, pH, TOC/TON, 13C/12C isotopes, and nutrients. Biological parameters were also sampled, and included biogenic Si, chlorophyll-a, phaeopigments, and primary productivity.

  214. Lee, K., F.J. Millero, and R.H. Wanninkhof. The carbon dioxide system in the Atlantic Ocean. Journal of Geophysical Research, 102(C7):15,693-15,708, doi:10.1029/97JC00067 1997

    Abstract:

    During the National Oceanic and Atmospheric Administration's Ocean Atmosphere Carbon Exchange Study expedition in the eastern North Atlantic in summer 1993, measurements of four CO2 parameters, along with hydrographic properties, were made: fugacity of CO2, fCO2 (measured at 20°C and in situ); pH (measured at 20°C); total inorganic carbon, TCO2; and total alkalinity, TA. The major objective of this cruise was to establish a benchmark against which future measurements of the transient invasion of CO2 can be made. The large-scale distributions of surface water CO2 parameters were related to temperature and salinity in this region. The subsurface TA and TCO2 measurements were fitted to multiple linear functions of salinity, in situ temperature, apparent oxygen utilization, and silicate. The measurements of the inorganic carbon system were also used to examine the internal consistency of the carbonate system in this area. The measurements were internally consistent to ±1.3% in fCO2, ±0.006 in pH, ±3 µmol kg- 1 in TCO2, and ±3 µmol kg-1 in TA if proper carbonic acid dissociation constants are used for different input combinations. The thermodynamic constants of Goyet and Poisson (1989), Roy et al. (1993), Millero (1995), and Lee and Millero (1995) were most consistent with the measurements of pH (at 20°C), TCO2, and TA. However, if fCO2 (at 20°C) is used in thermodynamic calculations, the constants of Mehrbach et al. (1973) gave the best representation of measurements. The constants of Lee and Millero (1995) were also in reasonable agreement with these measurements.

  215. Masters, J.C., R.H. Wanninkhof, D.T. Ho, M. Steckley, R.A. Feely, and C. Cosca. Continuous air and surface seawater measurements of fCO2 on board the NOAA Ship Malcolm Baldrige around-the-world cruise in 1995. NOAA Data Report, ERL-AOML-31 (PB98-105950), 80 pp., 1997

    Abstract:

    From February 1995 through January 1996 the NOAA ship Malcolm Baldrige conducted scientific operations on an around-the-world tour. The majority of work occurred in the Indian Ocean. The CO2 groups of the National Oceanic and Atmospheric Administration's (NOAA) Atlantic Oceanographic and Meteorological Laboratory (AOML) and Pacific Marine Environmental Laboratory (PMEL) operated a continuously flowing partial pressure carbon dioxide analyzer. Samples were taken from both the surface water and the overlying atmosphere to determine carbon dioxide flux across the gas/water interface. Other parameters such as salinity, barometric pressure, and temperature were used to reduce the data and calculate the fugacity of CO2*. Total dissolved inorganic carbon (DIC) samples of surface water were also collected. Data were collected on each leg of the cruise. Leg 1 was a transit from Miami to Durban, South Africa. Leg 2 operated from Durban to Colombo, Sri Lanka. Leg 3 operated from Colombo to Muscat, Oman. Leg 4 operated from Muscat to Victoria, Seychelles. Leg 5 operated from Victoria to Muscat, Oman. Leg 6 operated from Muscat to Diego Garcia. Leg 7 consisted of a transit from Diego Garcia to Fremantle, Australia followed by the major scientific operations between Fremantle and Male, Maldive Islands. Leg 8 included another transit from Male to Darwin, Australia. Operations began after leaving Darwin and headed into the western equatorial Pacific. The ship inported in American Samoa and continued to Panama, Miami, Florida and finished in Charleston, South Carolina. Descriptions of sampling methods and graphical data summaries are given in this report.

  216. Slansky, C.M., R.A. Feely, and R.H. Wanninkhof. The stepwise linear regression method for calculating anthropogenic CO2 invasion into the North Pacific Ocean. In Biogeochemical Processes in the North Pacific, S. Tsunogai (ed.). Japan Marine Science Foundation, 70-79, 1997

    Abstract:

    No abstract.

  217. Takahashi, T., R.A. Feely, R.F. Weiss, R.H. Wanninkhof, D.W. Chipman, S.C. Sutherland, and T.T. Takahashi. Global air-sea flux of CO2: An estimate based on measurements of sea-air pCO2 difference. Proceedings, National Academy of Science, USA, 94:8292-8299, doi:10.1073/pnas.94.16.8292 1997

    Abstract:

    Approximately 250,000 measurements made for the pCO2 difference between surface water and the marine atmosphere, ΔpCO2, have been assembled for the global oceans. Observations made in the equatorial Pacific during El Niño events have been excluded from the data set. These observations are mapped on the global 4° × 5° grid for a single virtual calendar year (chosen arbitrarily to be 1990) representing a non-El Niño year. Monthly global distributions of ΔpCO2 have been constructed using an interpolation method based on a lateral advection-diffusion transport equation. The net flux of CO2 across the sea surface has been computed using ΔpCO2 distributions and CO2 gas transfer coefficients across sea surface. The annual net uptake flux of CO2 by the global oceans thus estimated ranges from 0.60 to 1.34 Gt-C • yr-1 depending on different formulations used for wind speed dependence on the gas transfer coefficient. These estimates are subject to an error of up to 75% resulting from the numerical interpolation method used to estimate the distribution of ΔpCO2 over the global oceans. Temperate and polar oceans of both hemispheres are the major sinks for atmospheric CO2, whereas the equatorial oceans are the major sources for CO2. The Atlantic Ocean is the most important CO2 sink, providing about 60% of the global ocean uptake, while the Pacific Ocean is neutral because of its equatorial source flux being balanced by the sink flux of the temperate oceans. The Indian and Southern Oceans take up about 20% each.

  218. Wanninkhof, R.H., G. Hitchcock, W.J. Wiseman, G. Vargo, P.B. Ortner, W.E. Asher, D.T. Ho, P. Schlosser, M.-L. Dickson, R. Masserini, K. Fanning, and J.-Z. Zhang. Gas exchange, dispersion, and biological productivity on the West Florida Shelf: Results from a Lagrangian tracer study. Geophysical Research Letters, 24(14):1767-1770, doi:10.1029/97GL01757 1997

    Abstract:

    A Lagrangian tracer study was performed on the West Florida Shelf in April 1996 using deliberately injected trace gases. Although such studies have been performed previously, this work is the first where the deliberate tracers, in conjunction with carbon system parameters, are used to quantify changes in water column carbon inventories due to air-sea exchange and net community metabolism. The horizontal dispersion and the gas transfer velocity were determined over a period of 2 weeks from the change in both the concentrations and the concentration ratio of the two injected trace gases, sulfur hexafluoride (SF6) and helium-3 (3He). Horizontal diffusion estimates were about an order of magnitude greater than calculated from empirical equations, and the difference is attributed to vertical shear. The second moment of the patch grew to 1.6 × 103 km2 over a period of 11 days. The gas transfer velocity, normalized to CO2 exchange at 20°C, was 8.4 cm hr-1 at an average wind speed, U10, of 4.4 m s-1 for the duration of the experiment, which is in good agreement with empirical estimates. Remineralization rates exceeded productivity, causing an increase in dissolved inorganic carbon of about 1 µmol kg-1 day-1 in the water column. During this period of senescence, 80% of the increase in inorganic carbon is attributed to community remineralization and 20% due to invasion of atmospheric CO2. This net remineralization is in accordance with in situ and on-deck incubation experiments.

  219. Asher, W.E., and R.H. Wanninkhof. The effect of breaking waves on the analysis of dual-tracer gas exchange measurements. Proceedings, Third International Symposium on Air-Water-Gas Transfer, Heidelberg, Germany, July 24-27, 1995. Aeon Verlag and Studio, 517-528, 1996

    Abstract:

    The dual-gaseous tracer technique is a new and reliable method for directly measuring air-sea gas transfer velocities. However, analysis of data from these experiments requires the assumption that the dependence of the transfer velocity on molecular diffusivity is constant. Modeling and laboratory studies indicate that this could be an invalid assumption when gas transfer through bubbles generated by breaking waves is a significant portion of the sea-to-air gas flux. Here, a parameterization of the transfer velocity in terms of wind speed and fractional area whitecap coverage is developed that includes the effects of bubble-mediated exchange processes. It is shown that transfer velocities estimated using this parameterization are consistent with available oceanic gas exchange measurements. The parameterization is then used to investigate the consequences of including whitecap-related transfer processes in the analyses of data derived from dual-tracer experiments. In the case of the tracer pair, sulfur hexafluoride and helium-3, it is shown that assuming a constant diffusivity dependence underestimates transfer velocities of helium-3 by up to 20% at high wind speeds. It is also shown that using the parameterization to normalize the transfer velocity for helium-3 to carbon dioxide results in a 6% decrease in the estimated transfer velocity compared to constant-diffusivity dependence estimates.

  220. Asher, W.E., B.J. Higgins, L.M. Karle, P.J. Farley, C.R. Sherwood, W.W. Gardiner, R.H. Wanninkhof, H. Chen, T.P. Lantry, M. Steckley, E.C. Monahan, Q. Wang, and P.M. Smith. Measurements of gas transfer, whitecap coverage, and brightness temperature in a surf pool: An overview of WABEX-93. Proceedings, Third International Symposium on Air-Water-Gas Transfer, Heidelberg, Germany, July 24-27, 1995. Aeon Verlag and Studio, 205-216, 1996

    Abstract:

    Toward a method for estimating air-sea gas transfer velocities, kL, from remote measurements of fractional area whitecap coverage, WC, a gas exchange experiment was conducted in an outdoor surf pool during the October 1993 Wave Basin Experiment (WABEX-93). For both spilling and plunging breaking waves, measurements were made of WC; air-water fluxes of carbon dioxide, helium, nitrous oxide, oxygen, and sulfur hexafluoride; microwave brightness temperature of the water surface, sigma; aqueous-phase turbulence velocities; and bubble size spectra. The data show that kL, scales as a common, linear relation with WC for both spilling and plungin breaking waves. The gas transfer data have been used to develop an empirical parameterization for predicting kL from WC, Schmidt number, and solubility.

  221. Clark, J.F., P. Schlosser, H.J. Simpson, M. Stute, R.H. Wanninkhof, and D.T. Ho. Relationship between gas transfer velocities and wind speeds in the tidal Hudson River determined by the dual tracer technique. Proceedings, Third International Symposium on Air-Water-Gas Transfer, Heidelberg, Germany, July 24-27, 1995. Aeon Verlag and Studio, 785-799, 1996

    Abstract:

    Gas transfer velocities were determined using the dual tracer technique (3He and SF6) for two 40-60 km reaches of the tidal Hudson River. The experiments were performed near Poughkeepsie, New York in 1993 and near Catskill, New York in 1994. During both experiments wind speeds were measured above the river. The shape of daily axial SF6 distributions and the evolution of peak concentrations followed patterns predicted by the one-dimensional advection-diffusion equation. Mean gas transfer velocities calculated from the 1994 data using the temporal change in SF6 inventory (4.6 ± 0.4 cm hr-1) and the tracer ration (5.3 ± 0.2 cm hr-1) are in good agreement, suggesting that the dual tracer technique yields reasonable results. The relationships between gas transfer velocity and wind speeds found during these experiments are very similar to those observed previously for lakes, suggesting that wind is the primary source of surface turbulence in these reaches of the tidal Hudson River. The results of the 1993 and 1994 experiments agree very well, indicating that the local geometry of the river is of secondary importance.

  222. Wanninkhof, R.H. W.E. Asher, and E.C. Monahan. The influence of bubbles on air-water-gas exchange: Results from gas transfer experiments during WABEX-93. Proceedings, Third International Symposium on Air-Water-Gas Transfer, Heidelburg, Germany, July 24-27, 1995. Aeon Verlag and Studio, 239-254, 1996

    Abstract:

    Bubble-mediated gas transfer velocities were determined in a freshwater surf pool during WABEX-93. Gas transfer of N2O, He, and SF6 were measured under eight different mechanically-generated, breaking-wave conditions. Contrary to gas transfer across an air-water interface, where the transfer is solely a function of surface turbulence and the molecular diffusion coefficient of the gas, exchange through bubbles is also a function of the solubility of the gas, bubble size, and bubble penetration depths. The relative rates of gas transfer through bubbles of N2O, CO2, He, and SF6 for the experiment are compared with models developed by Woolf (1995) and Keeling (1992). The model of Woolf shows reasonable agreement with the observed results while that of Keeling overpredicts the exchange of N2O. The trend suggests that in the surf pool experiments the solubility dependence of the model of Keeling is too strong while that of Woolf is slightly too weak compared to the observations.

  223. Wanninkhof, R.H., and M. Knox. Chemical enhancement of CO2 exchange in natural waters. Limnology and Oceanography, 41(4):689-697, 1996

    Abstract:

    Exchange of carbon dioxide (CO2) under low turbulence conditions and high pH can be enhanced by hydration reactions of CO2 with hydroxide ions and water molecules in the boundary layer.  A series of field experiments was performed on several lakes, including alkaline closed-basin lakes, using enclosures (helmets) to study the enhancement process in nature.  In addition, the enhancement of CO2 exchange was studied in laboratory experiments using freshwater and seawater.  The results of the experiments are compared with published theoretical calculations. Within the experimental uncertainties and shortcomings of the chemical enhancement models, reasonable agreement was observed between experimental and theoretical results for seawater.  The experiments indicate, in accordance with theory, that chemical enhancement has a minor effect on air-sea gas exchange of CO2 under average oceanic turbulence conditions.  However, for the equatorial CO2 source regions, with high temperatures and low winds, the calculated CO2 enhancement amounts to 4% to 8% of the total exchange. The observations on lakes show poorer agreement with models which is attributed to experimental uncertainty and poor characterization of the chemistry of the lake waters.  The experiments show that chemical enhancement of CO2 is ubiquitous for the alkaline close basin lakes with enhancements of up to a factor of three.

  224. Wanninkhof, R.H., R.A. Feely, H. Chen, C. Cosca, and P.P. Murphy. Surface water fCO2 in the eastern equatorial Pacific during the 1992-1993 El Niño. Journal of Geophysical Research, 101(C7):16,333-16,343, doi:10.1029/96JC01348 1996

    Abstract:

    The fugacity of CO2 in surface water (fCO2W) was measured in the eastern equatorial Pacific (EEP) during the boreal spring and fall of 1992 and in the spring of 1993. A prolonged El Niño occurred during this period with anomalously warm sea surface temperatures (SST) during the spring of 1992 and 1993. Correspondingly, the fCO2W values were lower than historical non-El Niño values at the equator. However, the fCO2W in the spring of 1993 was up to 50 µatm higher than in the spring of 1992, despite similar SSTs. The trend is attributed to the slower response times of factors causing fCO2W decrease compared to rapid increase of fCO2W by upwelling cold water with high carbon content and subsequent heating. During the fall of 1992, SSTs south of the equator were 5°C cooler than in the spring, which is indicative of vigorous upwelling of water with high CO2 content from below the thermocline. Decreases in fCO2W due to net biological productivity and gas exchange take of the order of months, causing the fCO2W levels during the spring of 1993 to be elevated compared to the spring of the previous year. Our data and data obtained in 1986 and 1989 along 110°W suggest that fCO2W maxima in the equatorial Pacific can be either associated with temperature minima or temperature maxima. Despite the multitude of factors which influence fCO2W, most of the variance can be accounted for with changes in nitrate and SST. A multilinear regression of fCO2W with SST and nitrate for the 1992 data has a standard error in predicted fCO2W of 10 µatm. Air-sea fluxes of CO2 in the EEP were estimated to be 30% higher in the spring of 1993 and 10% higher in the fall of 1992 than in the spring of 1992.

  225. Chen, H., R.H. Wanninkhof, R. Feely, and D. Greeley. Measurements of fugacity of carbon dioxide in seawater: An evaluation of a method based on infrared analysis. NOAA Technical Memorandum, ERL-AOML-85 (PB95-271029), 54 pp., 1995

    Abstract:

    An analysis system is described to measure the fugacity of CO2 (fCO2)1 in 500 mL of seawater (discrete samples) by infrared analysis. The unit has been used on oceanographic research cruises sponsored by the Ocean-Atmosphere Carbon Exchange Study (OACES) of NOAA since 1991 for a total of approximately 10,000 measurements. The precision of the analyses based on replicate samples during routine analysis is 0.2%. Precision is primarily limited by sample storage, and the difference between headspace gas and water CO2 concentrations prior to equilibration. The precision and accuracy of the instrument is estimated in several different ways. A preliminary side by side test of two different discrete fCO2 systems using an infrared (IR) analyzer and a gas chromatograph (GC) shows a variability of 0.8% without significant bias. For surface waters the discrete measurements are compared with measurements from a continuous flowing underway system which was deployed on all cruises. Select comparisons with fCO2 calculated from spectrophotometric pH and DIC (Total Dissolved Inorganic Carbon) measurements are performed. These comparisons are limited by uncertainty in the magnitude and the temperature dependence of the carbon and borate dissociation constants. Indirect comparisons are made with pCO2 measurements of Drs. Takahashi and Chipman of LDEO in the South Atlantic and equatorial Pacific (EqPac). Although the measurements were performed months (for the EqPac study in 1992) to years (for the South Atlantic study in 1989 and 1991) apart, some inferences can be made by normalizing the fCO2 values and by performing the comparison in property space. The comparison indicates that the precision of our system is comparable to that of the LDEO system. The surface values obtained from the LDEO system during EqPac are 1.5 to 3% lower. There is inconclusive evidence that some of the subsurface LDEO pCO2 values are lower as well. However, the comparison of subsurface values for the North Atlantic Deep Water in the South Atlantic study shows good agreement. Because of the current uncertainty in dissociation constants, there is no a priori way to determine which value is correct.

  226. Clark, J.F., P. Schlosser, R.H. Wanninkhof, H.J. Simpson, W.S.F. Schuster, and D.T. Ho. Gas transfer velocities for SF6 and 3He in a small pond at low wind speeds. Geophysical Research Letters, 22(2):93-96, doi:10.1029/94GL02410 1995

    Abstract:

    Gas transfer velocities for two gases, SF6 (sulfur hexafluoride) and 3He, were determined in a small pond by injecting a mixture of these gases into the water and monitoring the decline of their concentrations over the next eight days. For wind speeds between 1.5-2.5 m s-1, no variations of gas transfer velocity with wind speed could be resolved with our data. Gas transfer velocities at wind speeds greater than 3 m s-1 were substantially larger and consistent with other lake tracer experiments. From the ratio of gas transfer velocities for SF6 and 3He, we calculated the Schmidt number exponent to be 0.57 ± 0.07.

  227. Feely, R.A., R.H. Wanninkhof, C. Cosca, H. Chen, M.D. Steckley, and P. Murphy. Distributions of fCO2 in the eastern equatorial Pacific during and after the 1992-1993 El Niño: Global fluxes of carbon and its related substances in the coastal sea-ocean-atmosphere system. Proceedings, IGBP Symposium, Sapporo, Japan, November 1994. Hokkaido University, 360-367, 1995

    Abstract:

    As part of the U.S. JGOFS Equatorial Pacific Process Study, measurements of fCO2 were determined for the atmosphere and in the surface waters of the central and eastern equatorial Pacific during the spring and autumn of 1992 and 1993, and the spring of 1994 after the 1992-1993 ENSO event. Surface water fCO2 data indicate significant differences between the springtime El Niño conditions and the autumn post-El Niño conditions. The autumn fugacity (ΔfCO2) maxima were approximately 15-55 µatm higher than in the spring. The lower surface ΔfCO2 values in the spring data set were the result of: (1) advection of CO2-depleted water from the west at the equator near 170°W; and (2) reduced upwelling and lower ΔfCO2 distributions as consequence of lighter zonal winds in the eastern Pacific from 140°W to 110°W. In the spring of 1993 elevated sea surface temperatures were observed in spring of 1992. In spring 1994 sea surface temperatures were near the climatological mean and fCO2 levels were 70-90 µatm higher than the 1992 levels. These results clearly indicate that the largest sustained fCO2 variations in the eastern equatorial Pacific occur during ENSO events.

  228. Feely, R.A., R.H. Wanninkhof, C.E. Cosca, P.P. Murphy, M.F. Lamb, and M.D. Steckley. CO2 distributions in the equatorial Pacific during the 1991-1992 ENSO event. Deep-Sea Research, Part II, 42(2-3):365-386, doi:10.1016/0967-0645(95)00027-N 1995

    Abstract:

    As part of the U.S. JGOFS Equatorial Pacific Process Study, measurements of CO2 species concentrations were made in the atmosphere and in the surface waters of the central and eastern equatorial Pacific during the boreal spring and autumn of 1992. Surface water fCO2 data indicate significant differences between the springtime El Niño conditions and the autumn post-El Niño conditions. The autumn fugacity (ΔfCO2) maxima were approximately 15-55 µatm higher than in the spring. The lower surface DELTA fCO2 values in the spring data set were the result of: (1) advection of CO2-depleted water from the west at the equator near 170°W; and (2) reduced upwelling and lower ΔfCO2 distributions as a consequence of lighter zonal winds in the eastern Pacific from 140°W to 110°W. Assuming the springtime data are representative of the El Niño conditions and the autumn data are representative of the post-El Niño conditions, it is estimated that the net annual CO2 flux during the 1991-1992 ENSO period is 0.3 Gt C. Over 60% of this flux occurred during the four-month period in the autumn when ΔfCO2 values were close to normal. The net annual reduction of the ocean-atmosphere CO2 flux during the 1991-1992 El Niño is estimated to be on the order of 0.5-0.7 Gt C.

  229. Ffield, A., R.L. Molinari, W.D. Wilson, and R.H. Wanninkhof. Repeat hydrography along WHP lines 15°W, 17°N, and 11°W. International WOCE Newsletter, 20:23-24, 1995

    Abstract:

    No abstract.

  230. Lamb, M.F., T.P. Lantry, J.C. Hendee, K.E. McTaggart, P.P. Murphy, R.A. Feely, R.H. Wanninkhof, F.J. Millero, R.H. Byrne, E.T. Peltzer, and D. Frazel. Chemical and hydrographic measurements from the equatorial Pacific during boreal autumn 1992. NOAA Data Report, ERL-PMEL-56 (PB95-274809), 173 pp., 1995

    Abstract:

    In the boreal autumn of 1992, NOAA's Climate and Global Change Program sponsored a major cooperative effort with the U.S. JGOFS Program in the central and eastern equatorial Pacific to investigate the unique role of equatorial processes on CO2 cycling during and following the 1991-1992 ENSO event. Data were collected meridionally along four transects, generally between 10°N and 10°S. The first leg (Leg 3) included the 140°W and 125°W transects; the second leg (Leg 4) sampled along 110°W, and the third leg (Leg 5) included stations along 95°W and three short transects extending westward from the Peru coast. Chemical parameters sampled included fCO2, DIC, TAlk, pH, TOC, and nutrients. Ancillary measurements of salinity, temperature, and dissolved oxygen (DO) were also taken. Descriptions of sampling methods and data summaries are given in this report.

  231. Lantry, T.P., M.F. Lamb, J.C. Hendee, R.H. Wanninkhof, R.A. Feely, F.J. Millero, R. Byrne, E.T. Peltzer, W.D. Wilson, and G.A. Berberian. Chemical and hydrographic measurements from the equatorial Pacific during boreal spring 1992. NOAA Data Report, ERL-AOML-27 (PB95-227773), 134 pp., 1995

    Abstract:

    From February 24 to May 19, 1992, the National Oceanic and Atmospheric Administration's (NOAA) Climate and Global Change Program sponsored a major cooperative effort with the U.S. Joint Global Ocean Flux Study (U.S. JGOFS) to study the role of equatorial processes on CO2 cycling in the central and eastern equatorial Pacific during the 1991-1992 El Niño Southern Oscillation (ENSO) event. The NOAA Ship Malcolm Baldrige performed four transequatorial sections in the region, and this report presents hydrographic and chemical data from that cruise, including tables of the following data from each station: hydrography from each CTD cast at the bottle trip depths, dissolved oxygen, fCO2, DIC, pH, TAlk, nutrients, and TOC. Descriptions of the sampling techniques and analytical methods used in the collection and processing of these data are also presented.

  232. MacIntyre, S., R.H. Wanninkhof, and J.P. Chanton. Trace gas exchange across the air-water interface in fresh water and coastal marine environments. In Biogenic Trace Gases: Measuring Emissions from Soil and Water, P.A. Matson and R.C. Harriss (eds.). Blackwell Science, Cambridge, 52-97, 1995

    Abstract:

    No abstract.

  233. Wanninkhof, R.H., R.A. Feely, D.K. Atwood, G.A. Berberian, W.D. Wilson, P.P. Murphy, and M.F. Lamb. Seasonal and lateral variations in carbon chemistry of surface water in the eastern equatorial Pacific during 1992. Deep-Sea Research, Part II, 42(2-3):387-409, doi:10.1029/96JC01348 1995

    Abstract:

    During the (boreal) spring and fall of 1992, the NOAA Ocean-Atmosphere Carbon Exchange Study did an intensive survey of upper water column (2 values were significantly lower in the spring, while sea surface temperatures south of the equator were higher. The seasonal change in surface water chemistry at the equator is due to changes in upwelling of nutrient and carbon-enriched water. Oxygen and CO2 anomalies at the surface point to approximately a three-fold increase in upwelling of thermocline water in the fall compared to the spring. The large-scale spatial variations in the surface chemistry patterns remained unchanged between spring and fall. There was a westward decrease in surface-water carbon and nitrate concentrations and a strong north to south asymmetry with higher carbon and nitrate values south of the equator. This pattern is attributed to input of carbon and nutrients with the South Equatorial Current from the east. Using velocities obtained from surface drifter tracks, along with reasonable gas exchange estimates and a "Redfield analysis" to account for export biological production, this westward decrease in carbon and nutrients can be quantitatively accounted for in the region from 0°to 3°S and 110°W to 140°W in the spring. In the fall the calculated concentration decrease is greater than observed, which is attributed to input from local equatorial upwelling along the pathway of water transit.

  234. Clark, J.F., R. Wanninkhof, P. Schlosser, and H.J. Simpson. Gas exchange rates in the tidal Hudson River using a dual tracer technique. Tellus B, 46(4):274-285, doi:10.1034/j.1600-0889.1994.t01-2-00003.x 1994

    Abstract:

    Gas exchange rates have been determined in the tidal Hudson River by injecting two inert gases, 3He and sulfur hexafluoride (SF6), and monitoring their decline with time. Their distributions along the main axis of the river were approximately Gaussian and maximum concentrations of excess 3He and SF6 observed during each transect decreased from about 6500 × 10-16 cm3 STP g-1 and 250 ppt (part per trillion by volume), respectively, to values close to atmospheric equilibrium concentration were observed. After three days of mixing, tracer concentrations in bottom samples were 0-19% greater than in surface samples. Gas transfer velocities were calculated from the temporal change in the depth-averaged excess 3He/SF6 ratio from stations having maximum tracer concentrations. They ranged from 1.5 to 9.0 cm h-1 and correlated well with mean wind speed.

  235. Feely, R.A., R.H. Wanninkhof, C.E. Cosca, M.J. McPhaden, R.H. Byrne, F.J. Millero, F.P. Chavez, T. Clayton, D.M. Campbell, and P.P. Murphy. The effect of tropical instability waves on CO2 species distributions along the equator in the eastern equatorial Pacific during the 1992 ENSO event. Geophysical Research Letters, 21(4):277-280, doi:10.1029/93GL03212 1994

    Abstract:

    Tropical instability waves have been shown to have a major impact on the variability of temperature and nutrients along the equatorial wave guide. In order to assess the impact of these features on carbon species distributions during an ENSO event, sea surface temperature, salinity, sigma-t, nitrate, CO2 fugacity, total inorganic carbon, total alkalinity, and pH along the equator were measured from 130°W to 100°W during 8-15 May 1992. Concurrent moored measurements of surface currents and temperature were also made at 0°, 110°W. Results indicate that tropical instability waves, with periods of 15-20 days and zonal wavelengths of 700-800 km, controlled the observed spatial variability of the CO2 species, nitrate, and hydrographic parameters at the equator.

  236. Forde, E.B., J.C. Hendee, and R.H. Wanninkhof. Hydrographic, carbon dioxide, nutrient, and productivity measurements from the South Atlantic during July and August of 1991. NOAA Data Report, ERL-AOML-24 (PB94-180668), 96 pp., 1994

    Abstract:

    From July 11 to September 2, 1991, the National Oceanic and Atmospheric Administration's (NOAA) Carbon Dioxide (CO2) and Radiatively Important Trace Species (RITS) programs participated in an oceanographic research cruise conducted aboard the NOAA ship Malcolm Baldrige. This report presents the research from that cruise that was conducted for the CO2 program, which has recently been renamed the Ocean-Atmosphere Carbon Exchange Study (OACES). During leg 1 of this cruise (Fortaleza, Brazil to Montevideo, Uruguay), 33 CTD hydrographic casts and 17 Go-Flo™ hydrographic (productivity) casts were conducted. Samples were also collected while underway on leg 1, for the determination of the fugacity of CO2 (fCO2) of the air and surface water. Leg 2 (Montevideo, Uruguay to Fortaleza, Brazil) collected 21 days of underway fCO2 measurements, conducted five CTD hydrographic casts, and nine Go-Flo™ hydrographic (productivity) casts. This report contains tables of the following data: hydrography from each CTD cast at the bottle trip depths (including salinity, oxygen and nutrients), discrete carbon parameters, underway carbon parameter values, and data from productivity casts. Descriptions of the sampling techniques and analytical methods used in the collection and processing of these data are also presented in this report.

  237. Watson, A.J., C.S. Law, K.A. Van Scoy, F.J. Millero, W. Yao, G.E. Friederich, M.I. Liddicoat, R.H. Wanninkhof, R.T. Barber, and K.H. Coale. Minimal effect of iron fertilization on sea-surface carbon dioxide concentrations. Nature, 371(6493):143-145, doi:10.1038/371143a0 1994

    Abstract:

    It has long been hypothesized that iron concentrations limit phytoplankton productivity in some parts of the ocean. As a result, iron may have played a role in modulating atmospheric CO2 levels between glacial and interglacial times, and it has been proposed that large-scale deposition of iron in the ocean might be an effective way to combat the rise of anthropogenic CO2 in the atmosphere. As part of an experiment in the equatorial Pacific Ocean, we observed the effect on dissolved CO2 of enriching a small (8 × 8 km) patch of water with iron. We saw significant depression of surface fugacities of CO2 within 48 hours of the iron release, which did not change systematically after that time. But the effect was only a small fraction (similar to 10%) of the CO2 drawdown that would have occurred had the enrichment resulted in the complete utilization of all the available nitrate and phosphate. Thus artificial fertilization of this ocean region did not cause a very large change in the surface CO2 concentration, in contrast to the effect observed in incubation experiments, where addition of similar concentrations of iron usually results in complete depletion of nutrients. Although our experiment does not necessarily mimic all circumstances under which iron deposition might occur naturally, our results do not support the idea that iron fertilization would significantly affect atmospheric CO2 concentrations.

  238. Bliven, L.F., J.-P. Giovanangeli, R.H. Wanninkhof, and B. Chapron. A laboratory study of friction-velocity estimates from scatterometry: Low and high regimes. International Journal of Remote Sensing, 14(9):1775-1785, doi:10.1080/01431169308954001 1993

    Abstract:

    Measurements from scatterometers pointing at wind-waves in three large wave-tanks are examined to study fetch effects and the correlation with wind friction-velocity u*. Time-series measurements were made at 13, 35, and 95 m with a Ka-band scatterometer aimed upwind at 30° incidence angle and vertical polarization. Average normalized radar cross-section sigmao values from all fetches follow a common trend for sigmao as a function of u*, so the fetch dependence is negligible. An empirical power-law model yields a high correlation between sigmao and u*, but because systematic anomalies arise, we re-examine a turbulence approach that delineates low and high regimes with a transition at u* of approximately 25 cm s-1. Using this criteria, the data are well represented by a two-section power-law relationship between sigmao and u*.

  239. Millero, F.J., R.H. Byrne, R.H. Wanninkhof, R.A. Feely, T. Clayton, P. Murphy, and M.F. Lamb. The internal consistency of CO2 measurements in the equatorial Pacific. Marine Chemistry, 44(2-4):269-280, doi:10.1016/0304-4203(93)90208-6 1993

    Abstract:

    During a recent NOAA JGOFS equatorial Pacific cruise, all four analytical parameters of the carbonate system were measured: pH, total alkalinity (TA), total carbon dioxide (TCO2), and the fugacity of carbon dioxide (fCO2). The measurements made during leg 2 on surface waters have been used to examine the internal consistency of the carbon dioxide system in these waters. The internal consistency of the measurements was examined by using various inputs of the measured parameters (pH-TA, pH-TCO2, pH-fCO2, fCO2-TCO2, and TA-TCO2) to calculate the components of the CO2 system. The results indicate that the measurements have an internal consistency of ±0.003-0.006 in pH, ±5-7 µmol kg-1 in TCO2, and ±6-9 µAtm in fCO2 if reliable constants are used for the dissociation of carbonic acid in seawater. These results indicate that our present understanding of the thermodynamics of the carbonate system in seawater is close to the present accuracy in measuring the various parameters of the system (±0.0002 in pH, ±4 µmol kg-1 in TA, ±2 µmol kg-1 in TCO2, and ±2 µAtm in fCO2).

  240. Wanninkhof, R.H., and K. Thoning. Measurement of fugacity of CO2 in surface water using continuous and discrete sampling methods. Marine Chemistry, 44(2-4):189-204, doi:10.1016/0304-4203(93)90202-Y 1993

    Abstract:

    Instrumentation and methodology is described which is used for measurement of the fugacity (or partial pressure) of carbon dioxide (fCO2 or pCO2) in surface seawater. Two separate instruments were developed for the measurements. One is an underway system which measures the mixing ratio of CO2, XCO2, in a headspace in equilibrium with surface seawater continuously pumped into a 24 l-equilibrium chamber. The other is a discrete system in which 460 ml aliquots of water areequilibrated with a 120 ml headspace. Both systems use a non-dispersive infrared analyzer as detector. In the underway instrument the average XCO2 in the headspace of an equilibration chamber is measured at near in-situ temperature over 20 min each hour. At a cruising speed of 13 knots this translates into a space averaged fCO2 value over 8 km. The underway system is ideally suited for mapping of the surface water fugacity over large geographic regions. Samples from the discrete instrument are analyzed at 20°C. The primary function of the system is for measurement of CO2 and other (carbon) parameters sub-sampled from the same aliquot. To calculate the fCO2 in water for in-situ conditions from the mixing ratio in the headspace of the flask of the discrete system, small carbon mass balance and, sometimes significant, temperature corrections have to be applied. Comparison of 100 surface values obtained in the South Atlantic using the underway and discrete systems shows that the average difference of pCO2 values for the two systems ranges from -4.3 µatm to -8.6 µatm, depending on the temperature correction, with a standard deviation of 4 µatm. The differences show scatter of up the 15 µatm which we attribute to a mismatch between the point samples for the discrete system and the integrated samples for the underway system.

  241. Wanninkhof, R.H., W.E. Asher, R. Weppernig, H. Chen, P. Schlosser, C. Langdon, and R. Sambrotto. Gas transfer experiment on Georges Bank using two volatile deliberate tracers. Journal of Geophysical Research, 98(C11):20,237-20,248, doi:10.1029/93JC01844 1993

    Abstract:

    A gas exchange experiment was performed on Georges Bank using the deliberate tracers sulfur hexafluoride (SF6) and helium 3 (3He). The concentrations of the tracers were measured in the water column over a period of 10 days. During this time the patch grew from an 8-km-long injection streak to an area of about 500 km2. The gas transfer velocity was determined from the change in the ratio of the tracers over time scaled to the ratio of their Schmidt numbers. A near-linear relationship between gas exchange and wind speed was observed based on four experimental points covering a wind speed range from 3 to 11 m/s. The results fall in the upper part of the range of gas transfer-wind speed relationships developed to date. Wind speeds during the experiment obtained from anemometers on the ship, on a free floating drifter, and on a fixed mooring showed significant differences. With the ability to measure gas transfer velocities over the ocean on time scales of several days, accurate wind speed/stress measurements are imperative to obtain a robust relationship between gas transfer and wind speed.

  242. Asher, W.E., P.J. Farley, R.H. Wanninkhof, E.C. Monahan, and T.S. Bates. Laboratory and field experiments on the correlation of fractional area whitecap coverage with air/sea gas transport. In Precipitation Scavenging and Atmosphere Surface Exchange, Volume 2, The Semonin Volume: Atmosphere Surface Exchange Processes, S.E. Schwartz and W.G.N. Slinn (eds.). Hemisphere Publishing Corporation, Washington, D.C., 815-828, 1992

    Abstract:

    Laboratory results have demonstrated that bubble plumes are a very efficient air/water gas transport mechanism. Because breaking waves generate bubble plumes, it may be possible to correlate air/sea gas transport velocities with whitecap coverage. This correlation may then allow transport velocities to be predicted from measurements of apparent microwave brightness temperature through the increase in sea surface microwave emissivity associated with breaking waves. In order to develop this remote-sensing based method for predicting air/sea gas fluxes, the whitecap simulation tank at Battelle/Marine Sciences Laboratory was used to measure transport velocities for oxygen, helium, sulfur hexafluoride, and dimethyl sulfide. This allowed the gas exchange process to be studied as a function of fractional areabubble plume coverage, molecular diffusivity (or Schmidt number), and water temperature. Using these results, an empirical model has been developed that permits prediction of the transport velocity in the Whitecap Simulation Tank from bubble plume coverage and Schmidt number. The implications of these results to the analysis of in situ dual-tracer air/sea gas transport dataare also discussed.

  243. Murray, J.W., M.W. Leinen, R.A. Feely, J.R. Toggweiler, and R. Wanninkhof. EqPac: A process study in the central equatorial Pacific. Oceanography, 5(3):134-143, doi:10.5670/oceanog.1992.01. 1992

    Abstract:

    EqPac is the United States-Joint Global Ocean Flux Study (US-JGOFS) process study in the central equatorial Pacific. The first EqPac cruises sailed in January 1992 during a moderately strong El Niño. This was fortuitous for our studies of chemical and biological distributions because El Niño events are difficult to predict, and the lead time for a project of this size is long. There was virtually no previous upper-water-column chemical or biological data for El Niño conditions in the central equatorial Pacific. Now an El Niño has been studied in considerable detail, and it will be easy to sample the extremes in environmental conditions by sampling non-El Niño conditions (including La Niña) in 1993 and the years thereafter. The implementation of EqPac illustrates how difficult it is to mount a large-scale interdisciplinary study of the ocean when the interannual variability is large.

  244. Wanninkhof, R.H. Relationship between gas exchange and wind speed over the ocean. Journal of Geophysical Research, 97(5):7373-7382, doi;10.1029/92JC00188 1992

    Abstract:

    Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean. The effect of these parameters is illustrated using a quadratic dependence of gas exchange on wind speed which is fit through gas transfer velocities over the ocean determined by the natural-14C disequilibrium and the bomb-14C inventory methods. Some of the variability between different data sets can be accounted for by the suggested mechanisms, but much of the variation appears due to other causes. Possible causes for the large difference between two frequently-used relationships between gas transfer and wind speed are discussed. To determine fluxes of gases other than CO2 across the air-water interface, the relevant expressions for gas transfer, and the temperature and salinity dependence of the Schmidt number and solubility of several gases of environmental interest, are included in an appendix.

  245. Oxburgh, R., W.S. Broecker, and R.H. Wanninkhof. The carbon budget of Mono Lake. Global Biogeochemical Cycles, 5(4):359-372, doi:10.1029/91GB02475 1991

    Abstract:

    Radiocarbon measurements suggest that 14C-free carbon enters from beneath Mono Lake at a rate of about 1 mol/m2/yr. An input of this magnitude should be manifested in the inorganic carbon budget of the lake and, with this in mind, we have devised a model to reconstruct the evolution of the partial pressure of CO2 (pCO2) over the past 150 years. This encompasses a period (1945 to present) during which major diversions of source water via the Los Angeles aqueduct have been in effect, significantly increasing the salinity of the lake and,hence, its pCO2. The model has been constrained by experimental characterization of the carbonate chemistry of the lake water, by the temperature dependence of pCO2 for the lake water, and by pCO2 measurements made on the lake water in 1966, 1969, 1981, and 1989. Our calculations suggest that prior to 1945 the pCO2 of about 3.3 mol/m2/yr is required. Volcanic activity beneath the lake is a probable source of this input.

  246. Wanninkhof, R.H., and L.F. Bliven. Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank. Journal of Geophysical Research, 96(C2):2785-2796, doi:10.1029/90JC02368 1991

    Abstract:

    Gas transfer velocities across the air-water interface are correlated with wind speed, friction velocity, and radar backscatter from the surface in a large wind-wave tank in Delft, The Netherlands. The rates of sulfur hexafluoride and nitrous oxide exchange were measured at wind speeds ranging from 3.5 m/s to 20 m/s, and with mechanically generated waves in the 100 m long, 8 m wide, and 0.7 m deep tank. Gas transfer velocities were related to wind speed with a power law dependence. Gas transfer showed a linear dependence with friction velocity. An exponential relationship between gas transfer and average radar backscatter cross section fits the wind tunnel data well for microwave units operating at 13.5 and 35 GHz in VV and HH polarization. The relative rates of gas exchange of the two gases confirm an inverse square root dependence on the Schmidt number at intermediate wind speeds. A slight enhancement of sulfur hexafluoride exchange compared to nitrous oxide exchange was evident when breaking waves were present.

  247. Wanninkhof, R.H., J.R. Ledwell, and A.J. Watson. Analysis of sulfur hexafluoride in seawater. Journal of Geophysical Research, 96(C5):8733-8740, doi:10.1029/91JC00104 1991

    Abstract:

    Analysis procedures and instrumentation to measure low levels of sulfur hexafluoride in seawater are described. The minimum detectable level for a 500 mL sample is about 3 x10-17 mol/L. Concentrations from 1.5 to 300 x 10-15 mol/L can be measured with approximately 2% precision. The procedure includes a concentration step employing a trap of Porapak-Qc in a dry ice/2-propanol bath. The system has been used for tracer experiments in Santa Monica Basin and Santa Cruz Basin, and will be improved for future tracer release experiments in the deep ocean.