Ocean Overturning

Salt water is denser than fresh water, and therefore sinks. Cold water is denser than warm water, and likewise sinks. Consequently, fresh, warm water remains near the surface and salty, cold water sinks into the deep ocean. This produces the continual churning and movement that form a large set of the world’s ocean currents. Ocean water tends to sink at high latitudes, drawing warm water and heat poleward from low latitudes.