Thermohaline Conveyor
A global water circulation system driven by water temperature and salt-density that distributes water between the Earth’s oceans. Warmer water closer to the ocean’s surface travels from the northern Pacific Ocean, south through the Indian Ocean (where it is joined by more warm water), around the southern tip of Africa, and up to the northern Atlantic Ocean. At this point, the water cools and sinks toward the bottom of the ocean and travels back via the same path. The thermohaline conveyor is repsonsibile for bringing warmer, more temperate climate to most of Europe and has a profound effect on global climate.
In the past, when this system has slowed or stopped, the results were ice ages throughout Europe. Concern is rising that global climate change is again slowing this conveyor system and endangering ecosystems and economies in the EU.
Also called thermohaline circulation
It seems to me that the actual circulation patterns are not well understood. If you do an image search for “thermohaline circulation” you will find quite a few very different maps of the circulation patterns. The above map does not show the cold Humbolt or Namibian currents, both of which cause extreme desert conditions along the Chile and Namibian coast lines respectively. Nor does it accurately depict the Gulf stream as it flows up the eastern coast of north America. Indian ocean currents are not accurate either. Part of the difficulty is that a some level of detail there are actually reverses of current along a coast – which is obviously hard to show clearly on one map.