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2002 LAPCOD Meeting
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Directly-measured mid-depth circulation in the Northeastern North Atlantic Ocean
A.S. Bower, B. Le Cann, T. Rossby, W. Zenk, J. Gould, K. Speer, P.L. Richardson, M.D. Prater, H.-M. Zhang (presenter: Le Cann)
Woods Hole Oceanographic Institution
abower@whoi.edu(Abstract received 10/31/2002 for session A)
ABSTRACT
As part of a large international effort to directly observe the circulation throughout the subpolar North Atlantic Ocean, several research groups from the U.S., the U.K., Germany and France collaborated in a major initiative to measure the absolute velocity at two levels in the northeastern North Atlantic using acoustically-tracked subsurface floats. The northeastern North Atlantic is important to the thermohaline circulation as this is where warm subtropical water is transported to high latitudes. A total of 223 float tracks, representing 328 float-years of data, were combined to generate maps of mean absolute velocity and eddy kinetic energy at the Thermocline and Labrador Sea Water levels. We find that most of the mean flow transported northward by the North Atlantic Current at the thermocline level recirculated within the subpolar region, and relatively little entered Rockall Trough or the Nordic Seas. Saline Mediterranean Water reached high latitudes not by continuous, broad-scale, mean advection along the eastern boundary as previously described, but by a combination of narrow slope currents and mixing processes. At the Labrador Sea Water level, a strong, topographically-constrained current associated with the overflow of dense water from the Norwegian Sea flowed around the northwestern Iceland Basin along the continental slope and Reykjanes Ridge, and closed counterclockwise recirculations existed adjacent to this boundary current. At both levels, currents crossed the Mid-Atlantic Ridge, eastbound and westbound, preferentially over deep gaps in the ridge. The latter result demonstrates that seafloor topography can constrain even upper ocean circulation patterns, possibly limiting the oceans response to climate change.
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2002 LAPCOD Meeting, Key Largo, Florida, December 12-16, 2000