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{{short description|Directional mass flow of oceanic water generated by external or internal forces }}{{more citations needed|date=January 2014}}(File:Corrientes-oceanicas.png|thumb|upright=2|Ocean surface currents)(File:Perpetual Ocean.ogv|thumb|Distinctive white lines trace the flow of surface currents around the world.)(File:Ocean flows at surface and 2000 meters below sea level.webm|thumb|Visualization showing global ocean currents from January{{nbsp}}1, 2010, to December{{nbsp}}31, 2012, at sea level, then at {{cvt|2000|m|ft}} below sea level)File:Circulation of Ocean Currents Around the Western Antarctic Ice Shelves.ogv|thumb|Animation of circulation around ice shelves of AntarcticaAntarcticaAn ocean current is a continuous, directed movement of seawater 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, together with its extension the North Atlantic Drift, makes northwest Europe much more temperate for its high latitude than other areas at the same latitude. Another example is Lima, Peru, whose cooler subtropical climate contrasts with that of its surrounding tropical latitudes because of the Humboldt Current. Ocean currents are patterns of water movement that influence climate zones and weather patterns around the world. They are 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

File:CSIRO ScienceImage 11128 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.jpg|thumb|right|The bathymetry of the Kerguelen Plateau in the Southern Ocean governs the course of the Kerguelen deep western boundary currentKerguelen deep western boundary currentOcean 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 units of sverdrup (sv), where 1 sv is equivalent to a volume flow rate of {{convert|1000000|m3|ft3|abbr=on}} per second.Surface ocean currents (in contrast to subsurface ocean currents), make up only 8% of all water in the ocean, are generally restricted to the upper {{convert|400|m|ft|abbr=on}} 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.Surface currents are measured in units of meters per second (m/s) or in knots.WEB, What is a current?, NOAA’s National Ocean Service, 2009-03-01,oceanservice.noaa.gov/facts/current.html, 2023-03-14,

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,WEB,www.nationalgeographic.org/encyclopedia/current/#:~:text=or%20as%20lightning.-,Air%20Currents,flow%20in%20a%20certain%20direction, Current, National Geographic, www.nationalgeographic.org, 2 September 2011, 7 January 2021, and the Coriolis effect plays a major role in their development.WEB,dashamlav.com/ocean-currents-world-map-types-causes-characteristics/, Ocean Currents of the World: Causes, 29 August 2020, 2020-11-20, The Ekman spiral velocity distribution results in the currents flowing at an angle to the driving winds, and they develop typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere.WEB,oceanservice.noaa.gov/education/kits/currents/05currents1.html, Surface Ocean Currents, National Ocean Service, March 25, 2008, noaa.gov, National Oceanic and Atmospheric Administration, 2017-06-13, live,web.archive.org/web/20170706062957/https://oceanservice.noaa.gov/education/kits/currents/05currents1.html, July 6, 2017, 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

{{Further|Deep ocean water}}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. An international program called Argo began researching deep ocean currents with a fleet of underwater robots in the 2000s.The thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes.JOURNAL, Rahmstorf, S, The concept of the thermohaline circulation, Nature, 421, 699, 2003,www.pik-potsdam.de/~stefan/Publications/Nature/nature_concept_03.pdf, 12610602, 6924, 10.1038/421699a, 2003Natur.421..699R, 4414604, free, JOURNAL, Lappo, SS, On reason of the northward heat advection across the Equator in the South Pacific and Atlantic ocean, Study of Ocean and Atmosphere Interaction Processes, 1984, 125–9, Moscow Department of Gidrometeoizdat (in Mandarin), The adjective thermohaline derives from (wikt:thermo-|thermo-) referring to temperature and {{nowrap|-haline}} referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents (such as the Gulf Stream) travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes (forming North Atlantic Deep Water). This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of around 1000 years)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? upwell in the North Pacific.JOURNAL, 10.1175/JPO2699.1, Primeau, F, Characterizing transport between the surface mixed layer and the ocean interior with a forward and adjoint global ocean transport model, Journal of Physical Oceanography, 35, 4, 545–64, 2005, 2005JPO....35..545P, 130736022,escholarship.org/content/qt5f76r4wn/qt5f76r4wn.pdf?t=n3tp5j, Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth’s oceans a global system. On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe. As such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is imprecisely used to refer to the meridional overturning circulation, (MOC).(File:Meddes-20060320-browse.jpg|thumb|Coupling data collected by NASA/JPL by several different satellite-borne sensors, researchers have been able to “break through” the ocean’s surface to detect “Meddies” – super-salty warm-water eddies that originate in the Mediterranean Sea and then sink more than a half-mile underwater in the Atlantic Ocean. The Meddies are shown in red in this scientific figure.)(File:Recording Current Meter.jpg|thumb|left|70px|A recording current meter|alt=Device to record ocean currents)

Distribution

Currents of the Arctic Ocean

• {{annotated link|Baffin Island Current}}
• {{annotated link|Beaufort Gyre}}
• {{annotated link|East Greenland Current}}
• {{annotated link|East Iceland Current}}
• {{annotated link|Labrador Current}}
• {{annotated link|North Icelandic Jet}}
• {{annotated link|Norwegian Current}}
• {{annotated link|Transpolar Drift Stream}}
• {{annotated link|West Greenland Current}}
• {{annotated link|West Spitsbergen Current}}

Currents of the Atlantic Ocean

• {{annotated link|Angola Current}}
• {{annotated link|Antilles Current}}
• {{annotated link|Atlantic meridional overturning circulation}}
• {{annotated link|Azores Current}}
• {{annotated link|Benguela Current}}
• {{annotated link|Brazil Current}}
• {{annotated link|Canary Current}}
• {{annotated link|Cape Horn Current}}
• {{annotated link|Caribbean Current}}
• {{annotated link|East Greenland Current}}
• {{annotated link|East Iceland Current}}
• {{annotated link|Equatorial Counter Current}}
• {{annotated link|Falkland Current}}
• {{annotated link|Florida Current}}
• {{annotated link|Guinea Current}}
• {{annotated link|Gulf Stream}}
• {{annotated link|Irminger Current}}
• {{annotated link|Labrador Current}}
• {{annotated link|Lomonosov Current}}
• {{annotated link|Loop Current}}
• {{annotated link|North Atlantic Current}}
• {{annotated link|North Brazil Current}}
• {{annotated link|North Equatorial Current}}
• {{annotated link|Norwegian Current}}
• {{annotated link|Portugal Current}}
• {{annotated link|South Atlantic Current}}
• {{annotated link|South Equatorial Current}}
• {{annotated link|West Greenland Current}}
• {{annotated link|West Spitsbergen Current}}

Currents of the Indian Ocean

• {{annotated link|Agulhas Current}}
• {{annotated link|Agulhas Return Current}}
• {{annotated link|East Madagascar Current}}
• {{annotated link|Equatorial Counter Current}}
• {{annotated link|Indian Monsoon Current}}
• {{annotated link|Indonesian Throughflow}}
• {{annotated link|Leeuwin Current}}
• {{annotated link|Madagascar Current}}
• {{annotated link|Mozambique Current}}
• {{annotated link|North Madagascar Current}}
• {{annotated link|Somali Current}}
• {{annotated link|South Equatorial Current}}
• {{annotated link|Southwest Madagascar Coastal Current}}
• {{annotated link|West Australian Current}}

Currents of the Pacific Ocean

• {{annotated link|Alaska Current}}
• {{annotated link|Aleutian Current}}
• {{annotated link|California Current}}
• {{annotated link|Cape Horn Current}}
• {{annotated link|Cromwell Current}}
• {{annotated link|Davidson Current}}
• {{annotated link|East Australian Current}}
• {{annotated link|East Korea Warm Current}}
• {{annotated link|Equatorial Counter Current}}
• {{annotated link|Humboldt Current}}
• {{annotated link|Indonesian Throughflow}}
• {{annotated link|Kamchatka Current}}
• {{annotated link|Kuroshio Current}}
• {{annotated link|Mindanao Current}}
• {{annotated link|Mindanao Eddy}}
• {{annotated link|North Equatorial Current}}
• {{annotated link|North Korea Cold Current}}
• {{annotated link|North Pacific Current}}
• {{annotated link|Oyashio Current}}
• {{annotated link|South Equatorial Current}}
• {{annotated link|Subtropical Countercurrent}}
• {{annotated link|Tasman Front}}
• {{annotated link|Tasman Outflow}}

Currents of the Southern Ocean

• {{annotated link|Antarctic Circumpolar Current}}
• {{annotated link|Tasman Outflow}}
• {{annotated link|Kerguelen deep western boundary current}}

Oceanic gyres

• {{annotated link|Beaufort Gyre}}
• {{annotated link|Indian Ocean Gyre}}
• {{annotated link|North Atlantic Gyre}}
• {{annotated link|North Pacific Gyre}}
• {{annotated link|Ross Gyre}}
• {{annotated link|South Atlantic Gyre}}
• {{annotated link|South Pacific Gyre}}
• {{annotated link|Weddell Gyre}}

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.WEB, What Is the Gulf Stream? {{!, NOAA SciJinks – All About Weather |url=https://scijinks.gov/gulf-stream/ |access-date=2024-04-15 |website=scijinks.gov}} 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.

Ocean currents and climate change

As atmospheric temperatures continue to rise, this is anticipated to have various effects on the strength of surface ocean currents, wind-driven circulation and dispersal patterns.JOURNAL, Wilson, Laura J., Fulton, Christopher J., Hogg, Andrew McC, Joyce, Karen E., Radford, Ben T. M., Fraser, Ceridwen I., 2016-05-02, Climate‐driven changes to ocean circulation and their inferred impacts on marine dispersal patterns,onlinelibrary.wiley.com/doi/10.1111/geb.12456, Global Ecology and Biogeography, 25, 8, 923–939, 10.1111/geb.12456, 1466-822X, JOURNAL, Miller, Johanna L., 2017, Ocean currents respond to climate change in unexpected ways,pubs.aip.org/physicstoday/article/70/1/17/1040900, Physics Today, 70, 1, 17–18, JOURNAL, Peng, Qihua, Xie, Shang-Ping, Wang, Dongxiao, Huang, Rui Xin, Chen, Gengxin, Shu, Yeqiang, Shi, Jia-Rui, Liu, Wei, 2022-04-22, Surface warming–induced global acceleration of upper ocean currents,www.science.org/doi/10.1126/sciadv.abj8394, Science Advances, 8, 16, 10.1126/sciadv.abj8394, 2375-2548, 9020668, 35442733, Ocean currents play a significant role in influencing climate, and shifts in climate, in turn, impact ocean currents. Over the last century, reconstructed sea surface temperature data reveal that western boundary currents are heating at double the rate of the global average.JOURNAL, Wu, Lixin, Cai, Wenju, Zhang, Liping, Nakamura, Hisashi, Timmermann, Axel, Joyce, Terry, McPhaden, Michael J., Alexander, Michael, Qiu, Bo, Visbeck, Martin, Chang, Ping, Giese, Benjamin, 2012-01-29, Enhanced warming over the global subtropical western boundary currents,www.nature.com/articles/nclimate1353, Nature Climate Change, 2, 3, 161–166, 10.1038/nclimate1353, 1758-6798, 1912/5125, free, These observations indicate that the western boundary currents are likely intensifying due to this change in temperature, and may continue to grow stronger in the near future. Studies investigating international ocean current patterns have also suspected that anthropogenic climate change has accelerated upper ocean currents by 77%. Faster upper ocean currents are often associated with increased vertical stratification, as well as faster and stronger zonal currents.In addition to water surface temperatures, the wind systems are a crucial determinant of ocean currents.JOURNAL, Constantin, Adrian, 2021-01-02, Frictional effects in wind-driven ocean currents,www.tandfonline.com/doi/full/10.1080/03091929.2020.1748614, Geophysical & Astrophysical Fluid Dynamics, 115, 1, 1–14, 10.1080/03091929.2020.1748614, 0309-1929, free, Wind wave systems influence oceanic heat exchange, the condition of the sea surface, and can alter ocean currents.JOURNAL, Dobrynin, Mikhail, Murawski, Jens, Baehr, Johanna, Ilyina, Tatiana, 2015-02-15, Detection and Attribution of Climate Change Signal in Ocean Wind Waves,journals.ametsoc.org/view/journals/clim/28/4/jcli-d-13-00664.1.xml, Journal of Climate, 28, 4, 1578–1591, 10.1175/JCLI-D-13-00664.1, 0894-8755, In the North Atlantic, equatorial Pacific, and Southern Ocean, increased wind speeds as well as significant wave heights have been attributed to climate change and natural processes combined. In the East Australian Current, global warming has also been accredited to increased wind stress curls, which intensify these currents, and may even indirectly increase sea levels, due to the additional warming created by stronger currents.JOURNAL, Cai, W., Shi, G., Cowan, T., Bi, D., Ribbe, J., 2005-12-10, The response of the Southern Annular Mode, the East Australian Current, and the southern mid‐latitude ocean circulation to global warming,agupubs.onlinelibrary.wiley.com/doi/10.1029/2005GL024701, Geophysical Research Letters, 32, 23, 10.1029/2005GL024701, 0094-8276, As ocean circulation changes due to climate, typical distribution patterns are also changing. The dispersal patterns of marine organisms depend on oceanographic conditions, which as a result, influence the biological composition of oceans. Due to the patchiness of the natural ecological world, dispersal is a species survival mechanism for various organisms.JOURNAL, Kininmonth, Stuart, 2011-04-11, Dispersal connectivity and reserve selection for marine conservation,www.sciencedirect.com/science/article/abs/pii/S0304380011000445, Ecological Modelling, 222, 7, 1272–1282, With strengthened boundary currents moving toward the poles, it is expected that some marine species will be redirected to the poles and greater depths.JOURNAL, Vergés, Adriana, Steinberg, Peter D., Hay, Mark E., Poore, Alistair G. B., Campbell, Alexandra H., Ballesteros, Enric, Heck, Kenneth L., Booth, David J., Coleman, Melinda A., Feary, David A., Figueira, Will, Langlois, Tim, Marzinelli, Ezequiel M., Mizerek, Toni, Mumby, Peter J., 2014-08-22, The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts,royalsocietypublishing.org/doi/10.1098/rspb.2014.0846, Proceedings of the Royal Society B: Biological Sciences, 281, 1789, 20140846, 10.1098/rspb.2014.0846, 0962-8452, 4100510, 25009065, The strengthening or weakening of typical dispersal pathways by increased temperatures are expected to not only impact the survival of native marine species due to inability to replenish their meta populations but also may increase the prevalence of invasive species. In Japanese corals and macroalgae, the unusual dispersal pattern of organisms toward the poles may destabilize native species.JOURNAL, Kumagai, Naoki H., García Molinos, Jorge, Yamano, Hiroya, Takao, Shintaro, Fujii, Masahiko, Yamanaka, Yasuhiro, 2018-09-04, Ocean currents and herbivory drive macroalgae-to-coral community shift under climate warming,pnas.org/doi/full/10.1073/pnas.1716826115, Proceedings of the National Academy of Sciences, 115, 36, 8990–8995, 10.1073/pnas.1716826115, 0027-8424, 6130349, 30126981,

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. Using ocean currents to help their ships into harbor and using currents such as the gulf stream to get back home.WEB, Atlantic Ocean - Exploration, Currents, Marine Life {{!, Britannica |url=https://www.britannica.com/place/Atlantic-Ocean/Study-and-exploration |access-date=2024-04-20 |website=www.britannica.com }} The lack of understanding of ocean currents during that time period is hypothesized to be one of the contributing factors to exploration failure. The gulf stream and the Canary current keep western European countries warmer and less variable, while at the same latitude North America’s weather was colder.WEB, US Department of Commerce, National Oceanic and Atmospheric Administration, Boundary Currents - Currents: NOAA’s National Ocean Service Education,oceanservice.noaa.gov/education/tutorial_currents/04currents3.html#:~:text=The%20Gulf%20Stream%20is%20a,current%20is%20the%20Gulf%20Stream, 2024-04-20, oceanservice.noaa.gov, 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. The utilization of currents today can still impact global trade, it can reduce the cost and emissions of shipping vessels.JOURNAL, Chang, Yu-Chia, Tseng, Ruo-Shan, Chen, Guan-Yu, Chu, Peter C., Shen, Yung-Ting, November 2013, Ship Routing Utilizing Strong Ocean Currents,www.cambridge.org/core/journals/journal-of-navigation/article/abs/ship-routing-utilizing-strong-ocean-currents/02039ECA1A45DCDD0B7935C94F79CBB9, The Journal of Navigation, 66, 6, 825–835, 10.1017/S0373463313000441, 0373-4633, Ocean currents can also impact the fishing industry, examples of this include the Tsugaru, Oyashio and Kuroshio currents all of which influence the western North Pacific temperature, which has been shown to be a habitat predictor for the Skipjack tuna.JOURNAL, Ramesh, Nandini, Rising, James A., Oremus, Kimberly L., 2019-06-21, The small world of global marine fisheries: The cross-boundary consequences of larval dispersal,www.science.org/doi/10.1126/science.aav3409, Science, 364, 6446, 1192–1196, 10.1126/science.aav3409, 0036-8075, It has also been shown that it is not just local currents that can affect a country’s economy, but neighboring currents can influence the viability of local fishing industries.JOURNAL, Talley, Lynne D., April 1, 1995, North Pacific Intermediate Water in the Kuroshio/Oyashio Mixed Water Region,journals-ametsoc-org.ezp1.lib.umn.edu/view/journals/phoc/25/4/1520-0485_1995_025_0475_npiwit_2_0_co_2.xml, American Meteorological Society, 475–501, AMS Publications,

See also

• {{annotated link|Currentology}}
• {{annotated link|Deep ocean water}}
• {{annotated link|Fish migration}}
• {{annotated link|Geostrophic current}}
• {{annotated link|Latitude of the Gulf Stream and the Gulf Stream north wall index}}
• {{annotated link|List of ocean circulation models}}
• {{section link|Marine habitats|Ocean currents}}
• {{annotated link|Marine current power}}
• {{annotated link|Ocean gyre}}
• {{annotated link|Physical oceanography}}
• {{annotated link|Subsurface ocean current}}
• {{annotated link|Thermohaline circulation}}
• {{annotated link|Tidal current}}
• {{annotated link|Volta do mar}}

References

{{Reflist}}

Further reading

• JOURNAL, Hansen, B., Already the day after tomorrow?, Science, 305, 2004, 953–954, 10.1126/science.1100085, 15310882, Østerhus, S, Quadfasel, D, Turrell, W, 5686, 12968045,
• JOURNAL, Kerr, Richard A., A slowing cog in the North Atlantic ocean’s climate machine, Science, 304, 2004, 371–372, 10.1126/science.304.5669.371a, 15087513, 5669, 42150417,
• JOURNAL, Munday, Phillip L., Jones, Geoffrey P., Pratchett, Morgan S., Williams, Ashley J., Climate change and the future for coral reef fishes, Fish and Fisheries, 9, 3, 2008, 261–285, 10.1111/j.1467-2979.2008.00281.x, free, 2008AqFF....9..261M,
• JOURNAL, Rahmstorf, S., Thermohaline circulation: The current climate, Nature, 421, 699, 2003, 10.1038/421699a, 12610602, 6924, 2003Natur.421..699R, 4414604, free,
• JOURNAL, Roemmich, D., Physical oceanography: Super spin in the southern seas, Nature, 449, 2007, 34–35, 10.1038/449034a, 17805284, 7158, 2007Natur.449...34R, 2951110,

External links

{{Commons category|Ocean currents}}

• Current global map of sea surface currents

{{Ocean}}{{Physical oceanography}}{{Underwater diving|scidiv}}{{authority control}}