What does the weather do to the ocean currents?

Ocean water and currents affect the climate. It takes a greater amount of energy to change the temperature of water than land or air; water warms up and cools off much slower than land or air does. As a result, inland climates are subject to more extreme temperature ranges than coastal climates, which are insulated by nearby water. Over half the heat that reaches the earth from the sun is absorbed by the ocean's surface layer, so surface currents move a lot of heat. Currents that originate near the equator are warm; currents that flow from the poles are cold.

The Great Ocean Conveyor Belt

The great ocean conveyor belt is an example of a density-driven current. These are also called thermohaline currents, because they are forced by differences in temperature or salinity, which affect the density of the water.

The great ocean conveyor belt begins as the coolest of all currents - literally. At the beginning of the conveyor belt:

The Gulf Stream delivers warm, and relatively salty, surface waters north to the Norwegian Sea. There the water gives up its heat to the atmosphere, especially during the frigidly cold winters. The surface waters cool to near freezing temperatures, at which time they become denser than the waters below them and sink. This process continues making cold water so dense that it sinks all the way to the bottom of the ocean.

During this time, the Gulf Stream continues to deliver warm water to the Norwegian Sea on the surface. The water can't very well pile up in the Norwegian Sea, so the deep cold water flows southward. It continues to flow southward, passing the Equator, until it enters the bottom of the Antarctic Circumpolar current. It then drifts around Africa and Australia, until it seeps northward into the bottom of the Pacific.