What causes ocean currents?

Ocean currents result from two processes - the action of wind on the surface of the water, and from variation in water temperature that causes movement- a process known as convection. Convection occurs because the oceanic waters heat up becoming less dense. This water moves above the cooler water, and give off its heat to the surrounding environment. As it cools, it begins to sink, and the process begins again. Convection results in the continual circulation of ocean water on a global scale.

There are many factors that determine the strength of a current, as well as the route it will follow. Winds have the most important influence on the flow of currents, but tides, precipitation, evaporation rates, shape of the ocean floor, and inflow from rivers and adjacent seas are also important. The major currents in the North Atlantic Ocean flow along the eastern North American coast from the Gulf of Mexico to the tip of Labrador.