Atlantic South Current

The South Atlantic’s warm-water gyre turns counter-clockwise between South America and Africa. It is an anti-cyclonic circulation that dominates the subtropical part of the basin and gives surface water a broad, looping path. The gyre carries South Atlantic Central Water, and the Coriolis effect is the reason its direction is opposite to the clockwise movement of the corresponding northern gyre.

This upper circulation is only one layer of the ocean. Antarctic Intermediate Water originates in the circumpolar region near the Drake Passage and the Falkland Islands, while both it and the subtractropical system receive some contribution from the Indian Ocean. North Atlantic Deep Water flows southward beneath the subtropical thermocline. These inputs place the South Atlantic within a global exchange of upper, intermediate and deep water, connecting tropical warmth, southern cold origins and distant northern waters.

The seabed beneath the gyre also shapes that exchange. West Gondwana broke up in the Early Cretaceous to form the South Atlantic, and the Mid-Atlantic Ridge then marks the South American–African plate boundary. Secondary ridges divide the deep floor, while the Walvis Ridge and Rio Grande Rise form obstacles to currents. Transform faults interrupt the ridge and create passages for bottom water. The basin therefore joins a warm rotating surface to a deeper system of basins and barriers.