Wednesday, October 29, 2008

Ocean Current

An ocean current is any of the number of river-like, moving masses of water flowing in all oceans, each having a characteristic direction, length, depth, speed, and temperature. This great flow of global conveyor belts is caused by the planet rotation, the gravitation of the moon, the wind, temperature, and salinity differences. Warm ocean currents are corridors of warm water moving from the tropics poleward where they release energy to the air. Cold ocean currents are corridors of cold water moving from higher latitudes toward the equator where they absorb the energy received in the tropics as they cool the air above.

Although some ocean currents result from density and salinity variations of water, the major ocean currents are wind-driven currents. Surface currents make up about 10% of all the water in the ocean. These waters are the upper 400 meters of the ocean. Deep water currents make up the other 90% of the ocean; these waters move around the ocean basins by density driven forces and gravity. Density difference is a function of different temperatures and salinity.

Ocean currents can flow for thousands of kilometers. They are very important in determining the climates of the continents, especially those regions bordering on the ocean. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. Another example is the Hawaiian Islands, where the climate is cooler than the tropical latitudes in which they are located because of the California Current.