Atlantic South Current

The South Atlantic floor preserves the break-up of western Gondwana. South America and Africa once formed one landmass; during the Early Cretaceous they began to split through rifting, volcanic activity and seafloor spreading. The fit of their opposing coastlines was observed on early maps, although later reconstructions showed that deformation zones and internal rifts complicated the apparently simple join. Matching continental margins remain a visible record of that separation.

The Mid-Atlantic Ridge marks the spreading boundary between the later South American and African plates. It runs the length of the Atlantic and divides the ocean into two long halves. Transform faults cut across the ridge, while secondary ridges separate the deep basins within each half. In the South Atlantic, the Walvis Ridge and Rio Grande Rise form major obstacles to water movement. These ridges and fracture zones turn the seafloor into a series of linked barriers, passages and enclosed depths.

At the surface, the anti-cyclonic subtropical gyre turns counter-clockwise. South Atlantic Central Water originates within that circulation, while Antarctic Intermediate Water forms in the upper circumpolar region near the Drake Passage and the Falkland Islands. North Atlantic Deep Water moves south below the thermocline. Together, the ancient continental split, present-day spreading and layered ocean circulation give the basin a history that stretches from the formation of its margins to the movement of water across them.