Atlantic South Equatorial Current

The southern equatorial waters sit within the warm tropical reach of the Atlantic, where large circulating systems move water across regional boundaries. Farther south, the South Atlantic is dominated by an anticyclonic subtropical gyre, and its surface waters travel in a counter-clockwise direction under the influence of winds and the Coriolis effect. The northern side of this system draws from the tropics and eventually passes water toward the subtropics and higher latitudes.

That broad circulation joins waters of different origins. South Atlantic Central Water forms within the subtropical gyre, while Antarctic Intermediate Water comes from the upper layers of the circumpolar region near the Drake Passage and the Falkland Islands. Below the thermocline, North Atlantic Deep Water moves south through the same basin. These pathways create a layered ocean in which warm surface water, fresher intermediate water, and dense deep water coexist.

Mariners encountered the system through winds and currents that could speed a voyage or drive it away from its intended course. The circulation also carried heat, salt, oxygen, and nutrients between the tropics and the far south, making the region part of a much wider Atlantic network. The water masses remain distinct even where their routes lie close together.