Via PhysOrg:
... Here's how it works:
Basically, the oceans, together with the atmosphere, rebalance heat on
the planet. The sun shines on the Earth and heats up the tropics more
than the poles. Near the poles, the ocean is cold and the water sinks;
near the equator, the surface of the ocean is inviting and warm—and
floats on top of the colder deep water.
So the question is this: Where does the water that goes down come back
up?
Speer, Marshall and other oceanographers now believe that it comes back
up in the Southern Ocean surrounding Antarctica—not as much in the warm
oceans as had been previously thought.
"We're not saying that nothing comes up in the rest of the World Ocean,
just that the main thrust is in the Southern Ocean," Speer said. "To a
large extent it's driven by the wind."
Very strong winds, to be precise.
Read more at: http://phys.org/news/2012-08-ocean-currents.html#jCp
Read more at: http://phys.org/news/2012-08-ocean-currents.html#jCp