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.
Explanation: When a fluid is heated unevenly, it starts moving in convection cells, carrying thermal energy from its warmer parts to its colder parts. Such motion due to temperature differences is called a convection current. Ocean currents may be considered convection currents because warm water rises and cold water moves in to replace it. Warm currents carry thermal energy from warmer regions near the equator toward the poles. Cold currents move toward the equator, making the temperature there lower than it would be otherwise.
