Atlantic South Current

The South Atlantic is a deep basin between Africa and South America, broad enough to contain extensive abyssal plains and isolated rises. It forms the southern half of the Atlantic system and opens toward the Southern Ocean. Water from the tropics mixes into this basin from the north, while colder water masses arrive around the southern gateway; the result is an ocean whose surface latitude and deep structure do not tell the same story.

The South Atlantic records the breakup of West Gondwana during the Early Cretaceous. As South America and Africa separated, rifting, volcanism and seafloor spreading opened the basin and left matching stretches of continental margin on opposite sides. The Mid-Atlantic Ridge then follows the spreading boundary, dividing the ocean lengthwise. Secondary ridges and transform faults interrupt its line and divide the deep floor into separate basins, including barriers formed by the Walvis Ridge and Rio Grande Rise.

Above this floor, the South Atlantic is dominated by an anti-cyclonic subtropical gyre. Its counter-clockwise circulation gathers South Atlantic Central Water, while Antarctic Intermediate Water forms in the upper circumpolar region near the Drake Passage and the Falkland Islands. North Atlantic Deep Water moves southward beneath the subtropical thermocline. Surface warmth, intermediate salinity and deep return flows therefore connect tropical conditions, southern polar influences and the geological basin into one system.