Atlantic South Current

The South Atlantic forms a broad maritime link between South America and Africa and opens toward the ocean surrounding Antarctica. Its history as a route is tied to the recognition that the Atlantic and Indian oceans meet beyond the Cape of Good Hope. Vasco da Gama demonstrated this connection in 1498, and ocean currents soon became part of the practical geography of European voyages into the Indian Ocean.

At the surface, the South Atlantic is dominated by an anti-cyclonic subtropical gyre. Coriolis deflection gives the circulation a counter-clockwise direction. South Atlantic Central Water originates in this gyre, whose moving surface is partly masked by an Ekman layer produced by wind. Pedro Álvares Cabral’s westward contact with Brazil in 1500 shows how the gyre could affect an India-bound fleet. Indian Ocean water also reaches the South Atlantic through Agulhas leakage and rings, making the basin’s circulation more complicated than a closed loop.

The deep seabed adds another system of passages and constraints. The Mid-Atlantic Ridge divides the ocean lengthwise and is cut by transform faults through which deep water can move. West Gondwana’s Early Cretaceous breakup created the basin, while the Walvis Ridge and Rio Grande Rise then obstruct some deeper currents. North Atlantic Deep Water flows south beneath the subtropical thermocline. Navigators saw a route across the sea; beneath them lay a layered exchange of central, intermediate and deep waters.