According to the University of Southern California, the two types of ocean currents are surface currents, also know as surface circulation, and deep water currents also called thermohaline circulation. These currents make up 10 percent and 90 percent of all the water in the ocean respectively.Continue Reading
USC goes on to explain that the surface currents make up around 400 meters of the upper ocean. Its movement is controlled by solar heating, winds, gravity, and the Coriolis force, which causes water to move to the right in the northern hemisphere around water mounds known as gyres. Ocean surface winds push the water, creating friction between the wind and water that also has an effect on the deep water currents.
Conversely, according to NOAA, the surface ocean air is cooled by arctic temperatures near the pole in the North Atlantic, with the addition of salt left over from melting ice that raises the water's density, becomes heavier than the surface water and sinks into the oceanic basins at the bottom of the sea. These waters make up the deep-water currents. The water then moves south, past the equator where it eventually reaches the waters of the arctic where they cool and sink to the bottom again. As the water moves north again it warms and moves to the surface, and the process is repeated once the water again reaches the North Atlantic.Learn more about Earth Science