An ocean current is any more or less permanent or continuous, directed movement of ocean water that flows in one of the Earth's oceans. 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 somewhat cooler (sub-tropical) than the tropical latitudes in which they are located because of the California Current. However the importance of currents is also illustrated by the El Niņo, in which a temporary reversal of an ocean current causes devastating climatic changes along the west coast of South America. El Niņo effects spread as far as Australia.
Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere due to the coriolis effect. In wind driven currents the Ekman spiral effect results in the currents flowing at an angle to the driving winds.
Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation refers to the deep ocean density driven ocean basin currents. These currents that flow under the surface of the ocean, and are thus hidden from immediate detection, are called submarine rivers .
Ocean currents are also very important in the dispersal of many life forms. A dramatic example is the life-cycle of the eel.
Important currents include:
- Agulhas Current
- East Madagascar Current
- Somali Current
- Mozambique Current
- Leeuwin Current
- Indonesian Through-flow
- North Equatorial Current
- South Equatorial Current
- Indian Monsoon
See also
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