A circular rotation of surface water currents in an ocean basin. Gyres are the result of prevailing winds, the earth’s rotation, and deflection by land masses, and they occur in all the major oceans. In the northern hemisphere the gyres of the North Pacific and North Atlantic rotate in a clockwise direction, whereas in the southern hemisphere the direction of rotation is anticlockwise. These directional flows exchange warm water from the equator for cooler water from the poles and have a huge impact on the climate of adjoining land masses, as well as regulating temperature, salinity, and nutrients in the oceans.