The Structure and Transport of the Brazil Current Between 27 deg and 36 deg South
1991
Zemba, Jan C.
An analysis of four hydrographic sections from the Thomas Washington marathon cruises--27, 31, 34 and 36 deg S--identifies downstream changes in the Brazil Current. They detail the current's change from a relatively small (12 Sv) , near surface feature to a large (80 Sv), deep current. Growth comes from a recirculation cell, deepening shear and a deeper zero velocity surface (required if NADW is to flow south). A four layer, basinwide model at 31 deg S ties the size of the Brazil Current and recirculation to various limits on layer-to-layer exchanges south of the section. The resulting flow pattern is consistent with equatorward meridional heat flux in the South Atlantic. Qualitative downstream changes in the total potential vorticity illuminate the presence of both frictional and inertial flow regimes. The presence of a frictional regime at the inshore edge suggests that care should be taken in assuming that potential vorticity is conserved in western boundary currents. The final picture which emerges is not of a small, surface-trapped Brazil Current; rather, it is that of a classic western, boundary current, increasing in strength and depth before turning east into the interior ocean.
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