The global ocean circulation, a "conveyor belt" for heat. Although conventionally shown as a narrow current, in fact much of the water moves in broad ocean-spanning sheets and giant eddies. Earlier (1980s) versions of this image showed the circulation moving straight up the Atlantic, as some of it does. They also did not show the complicated rise, descent and circulation of water around Antarctica, which is still shown differently in different versions.

Source: WMO/UNEP