Deep Ocean Currents

At depths greater than about 400 to 800 meters, the oceans are not really affected by wind. The motion of deep ocean currents is driven by differences in density. Differences in density are in turn caused by differences in temperature and salinity. Cold salty water is denser than warm water with a lower salt content. Unlike surface circulation of ocean water, deep ocean circulation is extremely slow. However, both surface currents and deep ocean currents work together to drive the water of the world’s oceans on a never-ending journey around the globe. Click the image to learn about thermohaline circulation.

Compare what happens to water in the North Atlantic and the Pacific Oceans in the cycle of thermohaline circulation.

In the North Atlantic, water loses heat to the atmosphere, cools, and sinks, beginning its journey to the deep ocean. In the Pacific, the water is warmed by solar radiation, rises and begins moving back toward the North Atlantic.