An ocean current is the constant, guided flow of sea water caused by a combination of wind, wave breaking forces, cables, and variations in temperature and salinity. This influences weather patterns, ocean currents and even air travel.
Tides lead to short distances from coastal currents. The wave, which drags on to the surface of the water as it blows, however causes major surface ocean currents in the open ocean. In the same direction as the tide, the water begins to flow.
For example, predictable winds, called trade winds, are flowing from east to west over the Equator in the Northern Hemisphere. The winds drag water on the surface and generate currents. The Coriolis effect – which arises from the rotation of the Planet – deflects them as these currents flow to the west. Then the currents shift to the right, toward the north.
A new collection of winds, the West, drives the currents back east at around 30 degrees north, resulting in a closed, clockwise loop.
The same thing occurs in the southern hemisphere, below the equator, except that the Coriolis effect bends surface currents to the left creating a clockwise circuit.
Subtropical gyres are called broad rotating currents which commence close to the equator. There are five major gyres: The Subtropical Gyres North and South Pacific, the South Atlantic and North Subtropical Gyres, and the Subtropical Gyre Indian Ocean.
Water is always moving, not only as waves and tides. Sea currents run in predictable routes as large rivers. Some ocean currents flow deep within the sea. Some currents flow in short lines, others pass around whole ocean basins and even around the world.