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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.
Description
Ocean currents can flow for thousands of kilometres. 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.
Reasons for currents
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 imposed wind stresses. In wind driven currents the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the seasons, this is most notable in equatorial currents.
Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation, also known as the ocean's conveyor belt, 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. These are currently being researched by floating devices, which maintain their depth according to slightly differing densities of waters. Upwelling and downwelling areas in the oceans are areas, where significant vertical movement of ocean water is observed.
Significance to people and sea life
Knowledge of surface ocean currents is essential in reducing costs of shipping, since they reduce fuel costs. In the sail-ship era knowledge was even more essential. A good example of this is the Agulhas current, which long prevented Portuguese sailors from reaching India. Even today, the round-the-world sailing competitors employ surface currents to their benefit.
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:
Arctic Ocean
Atlantic Ocean
- Angola Current
- Antilles Current
- Benguela current
- Brazil Current
- Canary Current
- Cape Horn Current
- Caribbean Current
- East Greenland Current
- Falkland Current
- Gulf Stream
- Guinea Current
- Labrador Current
- North Atlantic Current
- North Brazil Current
- North Equatorial Current
- Norwegian Current
- Portugal Current
- South Atlantic Current
- South Equatorial Current
- Spitzbergen Current
- West Greenland Current
- West Wind Drift
Pacific Ocean
- Alaska Current
- Aleutian Current
- California Current
- Cromwell current (a deep current)
- East Australian Current
- Equatorial Counter Current
- Humboldt Current (or Peru Current)
- Kamchatka Current
- Kuroshio Current (or Japan Current, Kuro Siwo)
- Mindanao Current
- North Equatorial Current
- North Pacific Current (or North Pacific Drift)
- Oyashio Current (or Oya Siwo)
- South Equatorial Current
- West Wind Drift
Indian Ocean
- Agulhas Current
- East Madagascar Current
- Equatorial Counter Current
- Indonesian Through-flow
- Leeuwin Current
- Madagascar Current
- Mozambique Current
- Somali Current
- South Australian Counter Current
- South Equatorial Current
- Southwest and Northeast Monsoon Drift (or Indian Monsoon Current)
- West Australian Current
- West Wind Drift
Southern Ocean
See also
External links
- NOAA Ocean Surface Current Analyses - Realtime (OSCAR) Near-realtime Pacific Ocean Surface Currents derived from satellite altimeter and scatterometer data.
- RSMAS Ocean Surface Currents
Physical oceanography | Bodies of water | Ocean currents
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"Ocean current"