Ocean current

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An ocean current is continuous, directed movement of ocean water. Ocean currents are rivers of hot or cold water within the ocean. The currents are generated from the forces acting upon the water like the planet rotation, the wind, the temperature and salinity (hence isopycnal) differences and the gravitation of the moon. The depth contours, the shoreline and other currents influence the current's direction and strength.

Contents 1 Important currents 2 Background 3 Significance to people and sea life 4 Important currents 4.1 Arctic Ocean 4.2 Atlantic Ocean 4.3 Pacific Ocean 4.4 Indian Ocean 4.5 Southern Ocean 5 See also 6 External links

[edit] Important currents

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 (sub-tropical) than the tropical latitudes in which they are located because of the California Current.

[edit] Background

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 because of 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, which flow under the surface of the ocean and are thus hidden from immediate detection, are called submarine rivers. These are currently being researched by a fleet of underwater robots called Argo. Upwelling and downwelling areas in the oceans are areas where significant vertical movement of ocean water is observed.

Surface currents make up about 10% of all the water in the ocean. Surface currents are generally restricted to the upper 400 meters of the ocean. The movement of deep water in the ocean basins is by density driven forces and gravity. The density difference is a function of different temperatures and salinity. Deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase. The main causes of currents are: solar heating, winds and gravity.

Ocean currents are measured in Sverdrup with the symbol Sv, where 1 Sv is equivalent to a volume flow rate of 10⁶ cubic meters per second.

[edit] 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.

[edit] Important currents

Arctic Ocean East Greenland Current Norwegian Current Beaufort Gyre (water or ice flow) Transpolar Drift (water or ice flow) Atlantic Ocean Angola Current Antilles Current Baffin Island Current Benguela current Brazil Current Canary Current Cape Horn Current Caribbean Current East Greenland Current Falkland Current Gulf Stream Guinea Current Labrador Current Lomonosov current (a deep current) North Atlantic Current North Brazil Current Norwegian Current Portugal Current South Atlantic Current Spitsbergen 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 Antarctic Circumpolar Current Weddell Gyre Tasman Outflow

[edit] See also

• Gyre
• Hydrothermal circulation
• Thermohaline circulation
• Marine current power
• Water mass
• Rogue wave (oceanography)

[edit] 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
• Coastal Ocean Current Monitoring Program
• Ocean Motion and Surface Currents
• Data Visualizer from OceanMotion.org

v • d • e Oceanic Gyres North Pacific Gyre North Equatorial Current · Kuroshio Current · North Pacific Current · California Current South Pacific Gyre South Equatorial Current · East Australian Current · Antarctic Circumpolar Current · Humboldt Current North Atlantic Gyre North Equatorial Current · Gulf Stream · North Atlantic Current · Canary Current South Atlantic Gyre South Equatorial Current · Brazil Current · Antarctic Circumpolar Current · Benguela Current Indian Ocean Gyre South Equatorial Current · Agulhas Current · Antarctic Circumpolar Current · West Australian Current Non-tropical gyres Beaufort Gyre · Indian Monsoon Gyre · Antarctic Circumpolar Current · Antarctic gyres Key concepts Ocean current · Coriolis effect · Ekman transport · Thermohaline circulation · Atmospheric circulation · Gyre boundary currents Marine debris · Great Pacific Garbage Patch · Commons images