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Global Studies: 
AOML is conducting climate studies with global scope in order to better understand the global setting for regional signals, and how the regional signals contribute to global phenomena. Even strongly regional phenomena such as El Niņo-Southern Oscillation (ENSO) have clear and important expressions in the Atlantic and Indian Oceans. Other signals previously thought to be regional, such as the North Atlantic Oscillation (NAO), are linked to the opposite side of the Northern Hemisphere through polar vortex fluctuations. The role of the ocean in the control and modulation of atmospheric carbon dioxide (CO2) and other climatically relevant compounds including water, halocarbons (such as methyl bromide [CH3Br]), and carbon monoxide (CO) requires assessment of both surface fluxes and changes in inventories (atmospheric and oceanic) over time." Analysis of sensitivity of the relevant fluxes to seasonal and interannual variability in hydrographic properties is critical to make future projections of atmospheric changes of chemical species. Finally, the evolution of a global observation system to support these and other such studies, and operational climate prediction, requires the active participation of research entities such as AOML in partnership with operational centers such as NOAA/National Center for Environmental Prediction (NCEP). The AOML-based Global Ocean Observing System (GOOS) Center achieves this by assuring efficient acquisition and quality control of real-time data, and by developing and implementing new technologies for operational use.

Physical climate studies: Using data diagnostics, we have statistically separated and indexed global climate signals such as ENSO and the NAO (Figure 2). We have found that within the equatorial Pacific region called NINO3, the interannual, global ENSO signal can be discriminated from the mainly interdecadal "non-ENSO" component (Figure 3). When these components are separately projected onto the global atmospheric variability (NCEP reanalysis), surprising differences can be seen in the Walker and Hadley circulation anomalies as they relate to the ENSO and non-ENSO variability (Figure 4). The decadal to multidecadal (D2M) variability in the NINO3 region has anomalous Walker and Hadley associations (in the troposphere) that are nearly opposite to those of ENSO, over the global tropics. This raises some transcendental questions for future research regarding the relationships between ENSO and D2M, and suggests that the predictabilities emanating from ENSO and D2M must be considered separately and combined with care. In newly proposed work, we hope to combine modeling and data diagnostics in an attempt to see how the Atlantic sector is affected by, and feeds back on, such distinct climate modes. Why is the tropical North Atlantic variability quasi-independent of the tropical South Atlantic variability (non-dipole)? Does this follow from separate forcings by larger scale, independent tropospheric modes of variability? How is the tropospheric direct circulation altered in each case and how are those patterns related to known phenomena such as the NAO?

Global atmospheric chemistry and carbon cycle: Research on the global ocean carbon cycle has been collaborative work in estimating the anthropogenic carbon inventory based on hydrographic observations during the global CO2 survey sponsored by NOAA and the Department of Energy, and air-sea CO2 fluxes from observations of surface water pCO2 on NOAA research ships. The high quality data, together with innovative methods to correct historical data, has led to robust estimates of the penetration of anthropogenic carbon into the ocean (Figure 5, from Peng et al., 1998, Nature, 396, 560-563). This figure shows change between the surveys of 1978 and 1995 in the Indian Ocean at latitudes south of about 15°S. These methods are now being applied to make global anthropogenic carbon inventory estimates. To gain better understanding of shorter-term variations in air-sea CO2 fluxes, we've instituted an active program of measurements of pCO2 on ships and contributed to the first global monthly climatology of air-sea CO2 fluxes. The climatology was subsequently used to estimate the interannual variability in air-sea fluxes, suggesting significantly smaller year-to-year changes than from atmospheric inference. This issue of variability and trends is of importance to determine the controls of carbon sequestration by the ocean. A new technique has been developed to measure trace level nutrients in oligotrophic waters, and the new production can be estimated based on the diel cycle of nitrate in the euphotic zone on diurnal time scales.

The atmospheric chemistry effort at AOML has included an effort to measure and characterize the reactive nitrogen oxide gases in the marine environment. These gases play a critical role in the control of ozone formation in the troposphere, and their source/sink and concentration distributions are a critical input for global tropospheric chemical models. Recent field programs include the pre-Indian Ocean Experiment (INDOEX) and INDOEX cruises aboard the NOAA ships Malcolm Baldrige and Ronald H. Brown in 1995 and 1999, respectively. Results obtained in the former cruise have been incorporated into a photochemical box model which indicated the unexpected role of halogens (BrO, HOBr, HBr) in constraining the budget of ozone in the remote marine boundary layer. Preliminary results from the 1999 INDOEX cruise (http://www-indoex.ucsd.edu) showed a significant impact of air pollutants in this region.

Atmospheric methyl bromide (CH3Br), which is of both natural and anthropogenic origin, has been identified as a Class I ozone-depleting substance in the amended and adjusted Montreal Protocol on Substances that Deplete Stratospheric Ozone. With the role of the ocean in regulating the atmospheric burden of this and other halocarbons still uncertain, recent field, laboratory, and modeling studies conducted in collaboration with investigators from the Climate Monitoring and Diagnostics Laboratory (CMDL) and universities have been designed to help improve our understanding of this role (Figure 6). We are improving our understanding of how biological as well as chemical processes are important in the assessment of the ocean's ability to regulate atmospheric CH3Br and other halocarbons (POC11).

In 1995-1996, the biological oceanography group at AOML led an Arabian Sea expedition under the aegis of Global Ecosystem Dynamics and Coupling (GLOBEC), one of the National Science Foundation's Global Climate Change programs. Using a range of acoustic frequencies, fish and zooplankton signals were distinguished, permitting rigorous quantitative analysis of the effect of monsoonal upwelling upon plankton biomass. Recent investigations of local upwelling and current structure have focused upon the relationship between temperature and local production processes and have highlighted eddy processes and local topographic effects (http://www.aoml.noaa.gov/ocd/globec).

Future AOML research will support the objectives of national and international research programs. In particular, we will contribute to the objectives of the Carbon Cycle Science Plan and the Surface Ocean Lower Atmosphere Study (SOLAS) through continued examination of the role that the ocean plays in regulating climatically important trace gases. Improved surface trace gas flux estimates requires expanded monitoring of surface water pCO2 and halocarbon saturations, improved methods of interpolation, and better parameterization of air-sea gas fluxes. Understanding the processes controlling the surface water trace gas concentrations, such as improved understanding of nutrient dynamics, vertical diffusion, biological productivity, and biological degradation, are high priorities.

NOAA Global Ocean Observing System (GOOS) Center: NOAA is developing a new paradigm for operational oceanography by placing operational activities within research laboratories. A study using data provided by the global expendable bathythermograph (XBT) network illustrates how the synergy between operations and research functions (NOAA collects approximately 50% of the total global XBT profiles). Analysis such as the space-time diagram of subsurface temperature (Figure 7) was used to determine which transects should be continued until a global profiling float array is deployed (an operational goal) and continues to be used to study decadal signals in the ocean and possible interactions with atmospheric climate (a research goal).

The GOOS Center incorporates the activities of the Global Drifter Program, which provides leadership and services from instrument procurement to data delivery for the global drifter array (GDA) of about 800 surface drifters. Sea surface temperature (SST) observations from the GDA are essential for creating SST analyses which are used in the initialization of National Center for Environmental Prediction (NCEP) ENSO predictions. Winds and sea-level pressures from the GDA are increasingly used for marine, regional, and global forecasts. Surface currents from the GDA are used in ocean global circulation models verification and in climate research. Products from the Global Drifter Program include a surface current climatology for the tropical Pacific Ocean for ENSO studies. Higher resolution surface current climatologies are in the works for the California Current and the world for oil spill mitigation efforts by the Minerals Management Service and for search and rescue operations of the Coast Guard.

The GOOS Center is working to improve the use of data in ocean models for predicting seasonal-to-interannual climatic variability. Recent research has led to a widespread realization that ocean models can be greatly improved with the addition of salinity-depth information. In the absence of an adequate observing system for salinity, it is necessary to leverage other types of data. In and below the thermocline, temperature-salinity correlations can be used to exploit XBT data. Near the surface, sea surface salinity could be monitored inexpensively. Additional information is available from satellite altimetric inferences of dynamic height. Our examination of NCEP's model-based reanalysis has revealed that the salinity of the equatorial undercurrent is generally too fresh, a fact that might be attributable to the treatment of the Indonesian throughflow. A related activity is our National Oceanographic Partnership Program collaboration (AOML, University of Miami, Los Alamos National Laboratory, Naval Research Laboratory) for assimilating data into HYCOM, a model that is distinctly different from that used by NCEP, to produce an alternative 30-year reanalysis.

Future GOOS Center activities will include: (1) continued evaluation of the XBT network and identification of important climate signals; (2) new World-Wide Web products using the GOOS Center data to market the data and to monitor the state of the upper ocean; and (3) increased interactions with NCEP to improve data management methodology, efficacy of the observing network, and the forecast models.

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Last updated: 01/25/2001