thermohaline circulation (THC)

density-driven circulation system in the world's oceans. In the Atlantic, warm water flows northward in the surface ocean, loses heat to the overlying colder atmosphere, and becomes more dense. This water sinks in the North Atlantic, forming deepwater. Eventually, the deepwater is returned to the surface over broad areas around the globe and joins near-surface currents to be returned to the areas of deepwater formation. This circuit is sometimes referred to as the "ocean conveyor belt."