The eastern boundary of the Gulf Stream recirculation

Publication Type  Journal Article
Year of Publication  1996
Authors  Marchese, P. J.; Gordon, A. L.
Journal Title  Journal of Marine Research
Volume  54
Issue  3
Pages  521-540
Journal Date  May
ISBN Number  0022-2402
Accession Number  ISI:A1996UN28200006
Key Words  north-atlantic ocean; potential vorticity; statistical description; sofar floats; circulation; variability; salinity; water; gyre; temperature
Abstract  

A meridionally aligned thermocline front near 60W in the subtropical North Atlantic is revealed by the 1992 Trident data set. The front separates saltier thermocline water to the east from less salty water to the west. The eastern water is subjected to excess evaporation of the subtropics, while the western water is fed by lower salinity Gulf Stream water, which derives water from the wet tropical Atlantic. It is suggested that the front marks the eastern edge of the Gulf Stream recirculation cell, hence refer to it as the recirculation front. ?The surface layer displays a fan-like TIS scatter above the 18 degrees C Subtropical Mode Water, with the fresher surface water located west of the recirculation front, and a subsurface salinity maximum to the east. In the lower thermocline (8 to 12 degrees C) there is a step-like salinity increase of about 0.04 toward the east as measured along isotherms, producing two modes in the TIS scatter. At the intermediate water level (approximately in the 4 to 8 degrees C range) the extent of the low salinity Antarctic Intermediate Water and salty Mediterranean outflow water are also reflected in the position of the recirculation front. That the front marks the easternmost extent of the Gulf Stream recirculation is supported by the potential vorticity, which reveals a region of high homogeneous values within the recirculation cell. East of the front, the potential vorticity field is sloped along isopycnals indicating the meridional flow of the Sverdrup interior. Mapping of the recirculation front using archived data reveals that it extends deep into the subtropical convergence zone (STCZ), a region whose fronts have all been previously attributed to Ekman convergence.

Notes  

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