All the water in the sea is in constant circulation, moving about in an orderly, well defined pattern of currents. This directed motion of water that flows in oceans is referred to as ocean currents. Currents are found in almost all the sources of water say ponds, rivers etc. You might have experienced the local currents that pull you out of the sea when you are in the beaches. Prevailing winds are the main force that keeps the current in motion. The currents are generated by tide, wind, density difference, earth’s rotation and moon’s gravitation. Differences in density are a function of temperature and salinity.
Warm water holds less salt than cold water and so it is less dense and rises towards the surface. On the other hand, cold water being denser than warm water sinks. Thus cold water near poles sinks and flows beneath the ocean surface toward the equator. There it rises to replace warm water that are constantly being carried by the surface currents (currents that occur 100 meters deep or above) toward the poles.
Ocean currents can flow for thousands of kilometers. They have a significant impact on the movement of energy and moisture between the oceans and the atmosphere. It determines the climates of the continents, especially those regions bordering the ocean. For instance, the Gulf Stream is a warm current that originates in the Gulf of Mexico and moves north towards Europe. It is best known for making northwest Europe much more temperate than any other region at the same latitude.
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