Open AccessZonal circulation across 52°W in the North Atlantic
Author(s) -
Hall Melinda M.,
Joyce Terrence M.,
Pickart Robert S.,
Smethie William M.,
Torres Daniel J.
Publication year - 2004
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003jc002103
Subject(s) - geology , hydrography , acoustic doppler current profiler , geostrophic wind , oceanography , north atlantic deep water , current (fluid) , water mass , boundary current , ocean current , ridge , gulf stream , thermohaline circulation , mid atlantic ridge , advection , climatology , paleontology , physics , thermodynamics
In July–August 1997, a hydrographic/Acoustic Doppler Current Profiler (ADCP)/tracer section was occupied along 52°W in the North Atlantic as part of the World Ocean Circulation Experiment Hydrographic Program. Underway and lowered ADCP (LADCP) data have been used to reference geostrophic velocities calculated from the hydrographic data; additional (small) velocity adjustments provided by an inverse model, constraining mass and silicate transports in 17 neutral density layers, yield the absolute zonal velocity field for 52°W. We find a vigorous circulation throughout the entire section, with an unusually strong Gulf Stream (169 Sv) and southern Deep Western Boundary Current (DWBC; 64 Sv) at the time of the cruise. At the northern boundary, on the west side of the Grand Banks of Newfoundland, we find the westward flowing Labrador Current (8.6 Sv), whose continuity from the Labrador Sea, east of our section, has been disputed. Directly to the south we identify the slopewater current (12.5 Sv eastward) and northern DWBC (12.5 Sv westward). Strong departures from strictly zonal flow in the interior, which are found in the LADCP data, make it difficult to diagnose the circulation there. Isolated deep property extrema in the southern portion, associated with alternating bands of eastward and westward flow, are consistent with the idea that the rough topography of the Mid‐Atlantic Ridge, directly east of our section, causes enhanced mixing of Antarctic Bottom Water properties into overlying waters with distinctly different properties. We calculate heat and freshwater fluxes crossing 52°W that exceed estimates based on air‐sea exchanges by a factor of 1.7.