Category: Physical Oceanography

Kids Deploying Global Drifters

NOAA’s Array of Drifting Ocean Buoys

Drifting buoys are a primary tool used by the oceanographic community to measure ocean surface circulation at unprecedented resolution. A drifter is composed of a surface float, which includes a transmitter to relay data via satellite, and a thermometer that reads temperature a few centimeters below the air-sea interface. The surface float is tethered to a holey sock drogue (a.k.a. “sea anchor”), centered at 15 m depth. The drifter follows the ocean surface current flow integrated over the drogue depth.

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Altimetry-derived surface geostrophic currents (NOAA/AOML). Background color is the dynamic height. Image Credit: NOAA AOML.

Upcoming Observations with Underwater Gliders

Underwater glider SG610, deployed on July 14, is located in the Caribbean Sea. This glider navigated in a SW, then in a SE, and now in a SW direction since it was deployed. The temperature and salinity profile observations indicate that on July 25 this glider started sampling waters of a cyclonic eddy that is now centered at approximately 16.5°N, 67.5°W, and has a radius of ~0.75deg as derived from satellite altimetry observations. These profile observations show a decrease in the salinity maximum, and a shallowing of the depth of this maximum salinity and of the depth of the 26°C isotherm.

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Gliders lined up and ready for deployment. Photo Credit: NOAA.

Gliders Patrol Ocean Waters with a Goal of Improved Prediction of Hurricane Intensity

Scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory are in the Caribbean to launch two underwater gliders from a vessel off Puerto Rico to collect temperature and other weather data to improve hurricane forecasting.One of the gliders will collect observations in the Caribbean Sea, and another in the North Atlantic Ocean. They are positioned to operate over the next six months (June-November) collecting data in areas where hurricanes are common and areas where there is a lack of environmental data.

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(left) Location of the three repeat XBT transects (AX25, AX22, and IX28) in the Southern Ocean. (right) Altimetry-derived magnitude of surface geostrophic currents for November 10, 2010, showing the multi-front signature of the ACC, from which the SAF and APF are highlighted. Overlaid is the location of AX25 (gray line), and the location of these fronts for November 10, 2010 (shaded markers). Image Credit: NOAA AOML.

Wind forced variability of the Antarctic Circumpolar Current south of Africa between 1993 and 2010

Researchers from PhOD and from the University of Cape Town used temperature data from the AX25 repeat XBT transect (from South Africa to Antarctica) in combination with other hydrographic and satellite observations to report a mechanism by which local winds alter the structure of the Antarctic Circumpolar Current flow south of Africa.

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Composites of SST and surface wind anomalies for 21 canonical and 12 Modoki El Niño events running from the event peak in DJF to the following JJA. SST and wind vectors shown are significant at the 10% level based on a Student's one sample t test. Boxes in Figures 1a (1b) outline Niño-3 (El Niño Modoki) regions.Image Credit: NOAA AOML.

Impact of canonical and Modoki El Niño on tropical Atlantic SST

Results from research performed by Dillon Amaya, an undergraduate Hollings Scholar from Texas A&M University, were published recently in Journal of Geophysical Research. Dillon’s work was carried out in the Physical Oceanography Division of AOML during the summer of 2013 and focused on understanding the impacts of different types of El Niño events (“canonical” and “Modoki”) on sea surface temperatures in the tropical Atlantic. The main result from the research is that Modoki El Niño;s fail to produce significant warming in the tropical North Atlantic, in contrast to the well known warming following canonical events.

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In-situ surface current velocity from ADCP (red vectors) and CTD station markers are shown for the July 2010 survey. Marker colors indicate the station θ-S profile classification as either GCW, LCW, EFCW, Coastal Shelf Water (green), or mixed-interleaved (black). Stations lacking waters denser than σθ = 24.0 kg m-3 are shown as small black dots. Prototype profile locations are indicated by an "x" and an enlarged marker. Letters identify selected sections along the cruise track. Image Credit: NOAA AOML.

Oceanographic conditions in the Gulf of America in July 2010, during the Deepwater Horizon oil spill

Results from collaborative research conducted by AOML and NOAA’s Southeast Fisheries Science Center (SEFSC) in response to the 2010 Deepwater Horizon oil spill, were recently published in Continental Shelf Research (December, 2013). PhOD oceanographers R. Smith, E. Johns, G. Goni, J. Trinanes, and R. Lumpkin, in collaboration with other researchers at AOML (M. Wood, C. Kelble, and S. Cummings) and SEFSC (J. Lamkin and S. Privoznik) report on the surface and subsurface connectivity across the eastern Gulf of America (GOM) during July 2010.

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Distribution of long-term mean observed (a)-(b) and simulated (c)-(d) meridional velocity along 23°W and 10°W. Gray dots in (a)-(b) indicate statistically significant values. Contour interval is 2.5 cm s-1. Figure reproduced from Perez et al., (2013). Image Credit: NOAA AOML.

Mean Meridional Currents in the Central and Eastern Equatorial Atlantic

In an article recently published in Climate Dynamics (Perez et al., 2013) , scientists in PhOD (R. Perez, R. Lumpkin, C. Schmid) described for the first time the mean vertical and cross-equatorial structure of the upper-ocean meridional currents in the Atlantic cold tongue region, using in situ observations including drifters, Argo, shipboard/lowered ADCP, and moored ADCP. This study involves collaborations with scientists from the University of Miami, Scripps Institution of Oceanography, and several international institutions and makes use of data from several major tropical Atlantic field programs including NOAA’s PIRATA Northeast Extension.

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