Ocean current

The ocean currents.
Distinctive white lines trace the flow of surface currents around the world.
Visualization showing global ocean currents from Jan 01, 2010 to Dec 31, 2012 at sea level then at 2000 meters below sea level.
Animation of circulation around ice shelves of Antarctica.

An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, shoreline configurations, and interactions with other currents influence a current's direction and strength. Ocean currents are primarily horizontal water movements.

An ocean current flows for great distances and together they create the global conveyor belt, which plays a dominant role in determining the climate of many of Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel. For example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. Other example is Lima, Peru, where the climate is cooler, being sub-tropical, than the tropical latitudes in which the area is located, due to the effect of the Humboldt Current.

Function

The bathymetry of the Kerguelen Plateau in the Southern Ocean governs the course of the new current part of the global network of ocean currents (Source:CSIRO)

Surface oceanic currents are sometimes wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere due to imposed wind stresses. In these wind-driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of surface ocean currents move somewhat with the seasons; this is most notable in equatorial currents.

Deep ocean basins generally have a non-symmetric surface current, in that the eastern equatorward-flowing branch is broad and diffuse whereas the western poleward flowing branch is very narrow. These western boundary currents (of which the Gulf Stream is an example) are a consequence of the rotation of the Earth.

Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is also known as the ocean's conveyor belt (which refers to deep ocean density-driven ocean basin currents). These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection. Where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of underwater robots called Argo.

Surface currents make up only 8% of all water in the ocean, are generally restricted to the upper 400 m (1,300 ft) of ocean water, and are separated from lower regions by varying temperatures and salinity which affect the density of the water, which in turn, defines each oceanic region. Because the movement of deep water in ocean basins is caused by density-driven forces and gravity, deep waters sink into deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.

Ocean currents are measured in sverdrup (sv), where 1 sv is equivalent to a volume flow rate of 1,000,000 m3 (35,000,000 cu ft) per second.

Surface currents are found on the surface of an ocean, and are driven by large scale wind currents. They are directly affected by the wind—the Coriolis effect plays a role in their behaviours.[1]

Other Languages
العربية: تيار محيطي
asturianu: Corriente marina
azərbaycanca: Dəniz cərəyanları
Bân-lâm-gú: Iûⁿ-lâu
беларуская: Марскія цячэнні
bosanski: Morska struja
brezhoneg: Kasenn
čeština: Mořský proud
dansk: Havstrøm
eesti: Hoovus
Ελληνικά: Θαλάσσιο ρεύμα
Esperanto: Marfluo
euskara: Itsaslaster
français: Courant marin
한국어: 해류
hrvatski: Morska struja
Bahasa Indonesia: Arus air laut
íslenska: Hafstraumur
עברית: זרם ים
Kiswahili: Mkondo wa bahari
Kreyòl ayisyen: Kouran sifas
Кыргызча: Деңиз агымдары
latviešu: Okeāna straume
македонски: Морска струја
Bahasa Melayu: Arus lautan
Nederlands: Zeestroom
日本語: 海流
norsk: Havstrøm
norsk nynorsk: Havstraum
occitan: Corrent marin
oʻzbekcha/ўзбекча: Dengiz oqimlari
polski: Prąd morski
português: Corrente oceânica
română: Curent marin
Simple English: Ocean current
slovenčina: Morský prúd
slovenščina: Oceanski tok
српски / srpski: Морска струја
srpskohrvatski / српскохрватски: Morska struja
suomi: Merivirta
svenska: Havsström
українська: Морська течія
اردو: بحری رو
Tiếng Việt: Hải lưu
中文: 洋流