The intermediate depth circulation of the western South Atlantic

The subsurface oceanic circulation is an important part of the Earth climat e system. Subsurface currents traditionally are inferred indirectly from di stributions of temperature and dissolved substances, occasionally supplemen ted by current meter measurements. Neutrally-buoyant floats however, now en able us to obtain for the first time directly measured intermediate depth v elocity fields over large areas such as the western South Atlantic. Here, o ur combined data set provides unprecedented observations and quantification of key flow patterns, such as the Subtropical Gyre return flow (12 Sv; 1 S verdrup = 10(6)m(3)s(-1)), its bifurcation near the Santos Plateau and the resulting continuous narrow and swift northward intermediate western bounda ry current (4 Sv). This northward flowing water passes through complex equa torial flows and finally enters into the North Atlantic.