The Ocean Conveyor

A global system of currents, often called the Ocean Conveyor, carries warm surface waters from the tropics northward. At high latitudes, the waters cool, releasing heat to the atmosphere and moderating wintertime climate in the North Atlantic region. The colder (and denser) waters sink and flow southward in the deep ocean to keep the conveyor moving.  (Illustration by Jack Cook, Woods Hole Oceanographic Institution)