Ocean conveyor belt

The global recirculation of water masses that determines today's climate.

The conveyor belt is driven by the sinking of North Atlantic Deep Water (NADW) through cooling of the surface water in the Greenland and Labrador Seas. NADW flows southward through the Atlantic below a depth of 3000 m. When it reaches the Antarctic Circumpolar Current (ACC), some of it continues into the Indian and Pacific Oceans at depth, enters the Atlantic through the Drake Passage and returns to the North Atlantic. Most NADW, however, rises very close to the surface in the ACC, where it freshens considerably through contact with surface water and enters all three oceans as Antarctic Intermediate Water at depths of 700–1000 m. Antarctic Intermediate Water penetrates into the Northern Hemisphere, being slowly entrained by central water, the water mass above it. Pacific central water enters the Indian Ocean through the Indonesian Seas. It then joins Indian central water to flow eastward and then southward in the subtropical gyre. Agulhas Current eddies carry it into the Atlantic, where it moves northward with the Benguela and Brazil Currents and in the Gulf Stream system toward the Greenland and Labrador Seas to cool and sink again, thus completing the conveyor belt circulation.