Ocean current

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Ocean currents
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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

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

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
. Ocean currents are patterns of water movement that influence climate zones and weather patterns around the world. They’re primarily driven by winds and by seawater density, although many other factors – including the shape and configuration of the ocean basin they flow through – influence them. The two basic types of currents – surface and deep-water currents – help define the character and flow of ocean waters across the planet.

Causes

The bathymetry of the Kerguelen Plateau in the Southern Ocean governs the course of the Kerguelen deep western boundary current, part of the global network of ocean currents.[2][3]

Ocean dynamics define and describe the motion of water within the oceans. Ocean temperature and motion fields can be separated into three distinct layers: mixed (surface) layer, upper ocean (above the thermocline), and deep ocean. 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, which 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.

Wind driven circulation

Surface oceanic currents are driven by wind currents, the large scale prevailing winds drive major persistent ocean currents, and seasonal or occasional winds drive currents of similar persistence to the winds that drive them,

southern hemisphere.[6]
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 equator-ward flowing branch is broad and diffuse whereas the pole-ward flowing

western boundary current
is relatively narrow.

Thermohaline circulation

Deep ocean currents are driven by density and temperature gradients. This thermohaline circulation is also known as the ocean's conveyor belt. These currents, sometimes called submarine rivers, flow deep below 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[when?] being researched using a fleet of underwater robots called Argo.

The thermohaline circulation is a part of the large-scale ocean circulation that is driven by global

meridional overturning circulation
, (MOC).

Distribution

Currents of the Arctic Ocean

Currents of the Atlantic Ocean

Currents of the Indian Ocean

Currents of the Pacific Ocean

Currents of the Southern Ocean

Oceanic gyres

Effects on climate and ecology

Ocean currents are important in the study of marine debris, and vice versa. These currents also affect temperatures throughout the world. For example, the ocean current that brings warm water up the north Atlantic to northwest Europe also cumulatively and slowly blocks ice from forming along the seashores, which would also block ships from entering and exiting inland waterways and seaports, hence ocean currents play a decisive role in influencing the climates of regions through which they flow. Cold ocean water currents flowing from polar and sub-polar regions bring in a lot of plankton that are crucial to the continued survival of several key sea creature species in marine ecosystems. Since plankton are the food of fish, abundant fish populations often live where these currents prevail.

Ocean currents are also very important in the dispersal of many life forms. An example is the life-cycle of the European Eel.

Economic importance

Knowledge of surface ocean currents is essential in reducing costs of shipping, since traveling with them reduces fuel costs. In the wind powered sailing-ship era, knowledge of wind patterns and ocean currents was even more essential. A good example of this is the Agulhas Current (down along eastern Africa), which long prevented sailors from reaching India. In recent times, around-the-world sailing competitors make good use of surface currents to build and maintain speed. Ocean currents can also be used for marine power generation, with areas of Japan, Florida and Hawaii being considered for test projects.

See also

References

  1. ^ NOAA, NOAA. "What is a current?". Ocean Service Noaa. National Ocean Service. Retrieved 13 December 2020.
  2. ^ a b "Massive Southern Ocean current discovered". ScienceDaily. Apr 27, 2010.
  3. ^ .
  4. ^ "Current". www.nationalgeographic.org. National Geographic. 2 September 2011. Retrieved 7 January 2021.
  5. ^ "Ocean Currents of the World: Causes". 29 August 2020. Retrieved 2020-11-20.
  6. ^ National Ocean Service (March 25, 2008). "Surface Ocean Currents". noaa.gov. National Oceanic and Atmospheric Administration. Archived from the original on July 6, 2017. Retrieved 2017-06-13.
  7. S2CID 4414604
    .
  8. ^ Lappo, SS (1984). "On reason of the northward heat advection across the Equator in the South Pacific and Atlantic ocean". Study of Ocean and Atmosphere Interaction Processes. Moscow Department of Gidrometeoizdat (in Mandarin): 125–9.
  9. ^ The global ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity; What is the global ocean conveyor belt?
  10. S2CID 130736022
    .

Further reading

External links