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48-777: The South Atlantic Current is an eastward ocean current , fed by the Brazil Current . That fraction of it which reaches the African coast feeds the Benguela Current . It is continuous with the northern edge of the Antarctic Circumpolar Current . The seafaring is usually easier and thus safer in area of the South Atlantic Current than in the Antarctic Circumpolar Current, though also slower. It

96-1116: A Stream function ψ {\displaystyle \psi } and linearize by assuming that D >> h {\displaystyle D>>h} , equation (4) reduces to ∇ 2 ψ + α ( ∂ ψ ∂ x ) = γ sin ⁡ ( π y b ) ( 5 ) {\displaystyle \nabla ^{2}\psi +\alpha \left({\frac {\partial \psi }{\partial x}}\right)=\gamma \sin \left({\frac {\pi y}{b}}\right)\qquad (5)} Here α = ( D R ) ( ∂ f ∂ y ) {\displaystyle \alpha =\left({\frac {D}{R}}\right)\left({\frac {\partial f}{\partial y}}\right)} and γ = π F R b {\displaystyle \gamma ={\frac {\pi F}{Rb}}} The solutions of (5) with boundary condition that ψ {\displaystyle \psi } be constant on

144-543: A volume flow rate of 1,000,000 m (35,000,000 cu ft) per second. There are two main types of currents, surface currents and deep water currents. Generally surface currents are driven by wind systems and deep water currents are driven by differences in water density due to variations in water temperature and salinity . 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

192-417: A closed circulation for an entire ocean basin and to counteract the wind-driven flow. Sverdrup introduced a potential vorticity argument to connect the net, interior flow of the oceans to the surface wind stress and the incited planetary vorticity perturbations. For instance, Ekman convergence in the sub-tropics (related to the existence of the trade winds in the tropics and the westerlies in the mid-latitudes)

240-399: A decisive role in influencing the climates of regions through which they flow. Ocean currents are important in the study of marine debris . Upwellings and cold ocean water currents flowing from polar and sub-polar regions bring in nutrients that support plankton growth, which are crucial prey items for several key species in marine ecosystems . Ocean currents are also important in

288-1331: A linearized, frictional term to account for the dissipative effects that prevent the real ocean from accelerating. He starts, thus, from the steady-state momentum and continuity equations: f ( D + h ) v − F cos ⁡ ( π y b ) − R u − g ( D + h ) ∂ h ∂ x = 0 ( 1 ) {\displaystyle f(D+h)v-F\cos \left({\frac {\pi y}{b}}\right)-Ru-g(D+h){\frac {\partial h}{\partial x}}=0\qquad (1)} − f ( D + h ) u − R v − g ( D + h ) ∂ h ∂ y = 0 ( 2 ) {\displaystyle \quad -f(D+h)u-Rv-g(D+h){\frac {\partial h}{\partial y}}=0\qquad \qquad (2)} ∂ [ ( D + h ) u ] ∂ x + ∂ [ ( D + h ) v ] ∂ y = 0 ( 3 ) {\displaystyle \qquad \qquad {\frac {\partial [(D+h)u]}{\partial x}}+{\frac {\partial [(D+h)v]}{\partial y}}=0\qquad \qquad \qquad (3)} Here f {\displaystyle f}

336-461: A more realistic frictional term, while emphasizing "the lateral dissipation of eddy energy". In this way, not only did he reproduce Stommel's results, recreating thus the circulation of a western boundary current of an ocean gyre resembling the Gulf stream, but he also showed that sub-polar gyres should develop northward of the subtropical ones, spinning in the opposite direction. Observations indicate that

384-562: A much colder northern Europe and greater sea-level rise along the U.S. East Coast." In addition to water surface temperatures, the wind systems are a crucial determinant of ocean currents. Wind wave systems influence oceanic heat exchange, the condition of the sea surface, and can alter ocean currents. 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

432-453: 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. With strengthened boundary currents moving toward the poles, it is expected that some marine species will be redirected to the poles and greater depths. The strengthening or weakening of typical dispersal pathways by increased temperatures are expected to not only impact

480-418: 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. These observations indicate that the western boundary currents are likely intensifying due to this change in temperature, and may continue to grow stronger in

528-560: A simple, homogeneous, rectangular ocean model to examine the streamlines and surface height contours for an ocean at a non-rotating frame, an ocean characterized by a constant Coriolis parameter and finally, a real-case ocean basin with a latitudinally-varying Coriolis parameter. In this simple modeling the principal factors that were accounted for influencing the oceanic circulation were: In this, Stommel assumed an ocean of constant density and depth D + h {\displaystyle D+h} seeing ocean currents; he also introduced

SECTION 10

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576-507: Is a cold current. This article about a specific ocean current is a stub . You can help Misplaced Pages by expanding it . Ocean current Ocean currents flow 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

624-493: Is a constant, ocean circulation has no preference toward intensification/acceleration near the western boundary. The streamlines exhibit a symmetric behavior in all directions, with the height contours demonstrating a nearly parallel relation to the streamlines, in a homogeneously rotating ocean. Finally, on a rotating sphere - the case where the Coriolis force is latitudinally variant, a distinct tendency for asymmetrical streamlines

672-425: Is also known as the ocean's conveyor belt. Where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling . The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content , factors which together determine the density of seawater. The thermohaline circulation is a part of the large-scale ocean circulation that

720-524: Is driven by global density gradients created by surface heat and freshwater fluxes . 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 ,

768-458: Is found, with an intense clustering along the western coasts. Mathematically elegant figures within models of the distribution of streamlines and height contours in such an ocean if currents uniformly rotate can be found in the paper. The physics of western intensification can be understood through a mechanism that helps maintain the vortex balance along an ocean gyre. Harald Sverdrup was the first one, preceding Henry Stommel, to attempt to explain

816-456: Is the strength of the Coriolis force, R {\displaystyle R} is the bottom-friction coefficient, g {\displaystyle g\,\,} is gravity, and − F cos ⁡ ( π y b ) {\displaystyle -F\cos \left({\frac {\pi y}{b}}\right)} is the wind forcing. The wind is blowing towards

864-477: The Atlantic meridional overturning circulation (AMOC) is in danger of collapsing due to climate change, which would have extreme impacts on the climate of northern Europe and more widely, although this topic is controversial and remains an active area of research. The "State of the cryosphere" report, dedicates significant space to AMOC, saying it may be enroute to collapse because of ice melt and water warming. In

912-496: The East Australian Current , global warming has also been accredited to increased wind stress curl , which intensifies these currents, and may even indirectly increase sea levels, due to the additional warming created by stronger currents. 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

960-518: The Humboldt Current . The largest ocean current is the Antarctic Circumpolar Current (ACC), a wind-driven current which flows clockwise uninterrupted around Antarctica. The ACC connects all the ocean basins together, and also provides a link between the atmosphere and the deep ocean due to the way water upwells and downwells on either side of it. Ocean currents are patterns of water movement that influence climate zones and weather patterns around

1008-580: The Kuroshio Current . Low-latitude western boundary currents are similar to sub-tropical western boundary currents but carry cool water from the subtropics equatorward. Examples include the Mindanao Current and the North Brazil Current . Western intensification applies to the western arm of an oceanic current , particularly a large gyre in such a basin . The trade winds blow westward in

SECTION 20

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1056-434: The ocean warming over the subtropical western boundary currents is two-to-three times stronger than the global mean surface ocean warming. A study finds that the enhanced warming may be attributed to an intensification and poleward shift of the western boundary currents as a side-effect of the widening Hadley circulation under global warming. These warming hotspots cause severe environmental and economic problems, such as

1104-437: 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. Large scale currents are driven by gradients in water density , which in turn depend on variations in temperature and salinity. This thermohaline circulation

1152-455: 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). Since the 2000s an international program called Argo has been mapping the temperature and salinity structure of

1200-415: The coastlines, and for different values of α {\displaystyle \alpha } , emphasize the role of the variation of the Coriolis parameter with latitude in inciting the strengthening of western boundary currents. Such currents are observed to be much faster, deeper, narrower and warmer than their eastern counterparts. For a non-rotating state (zero Coriolis parameter) and where that

1248-544: The cost and emissions of shipping vessels. 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 . It has also been shown that it is not just local currents that can affect a country's economy, but neighboring currents can influence

1296-564: The dispersal and distribution of many organisms, inclusing those with pelagic egg or larval stages. An example is the life-cycle of the European Eel . Terrestrial species, for example tortoises and lizards, can be carried on floating debris by currents to colonise new terrestrial areas and islands . The continued rise of atmospheric temperatures is anticipated to have various effects on the strength of surface ocean currents, wind-driven circulation and dispersal patterns. Ocean currents play

1344-620: The eastern side of oceanic basins (adjacent to the western coasts of continents). Subtropical eastern boundary currents flow equatorward, transporting cold water from higher latitudes to lower latitudes; examples include the Benguela Current , the Canary Current , the Humboldt (Peru) Current , and the California Current . Coastal upwelling often brings nutrient-rich water into eastern boundary current regions, making them productive areas of

1392-497: The mid-ocean vorticity balance by looking at the relationship between surface wind forcings and the mass transport within the upper ocean layer. He assumed a geostrophic interior flow, while neglecting any frictional or viscosity effects and presuming that the circulation vanishes at some depth in the ocean. This prohibited the application of his theory to the western boundary currents, since some form of dissipative effect (bottom Ekman layer) would be later shown to be necessary to predict

1440-407: The moon in the form of tides , and by the effects of variations in water density. 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 units of sverdrup (Sv) , where 1 Sv is equivalent to

1488-462: The near future. There is evidence that surface warming due to anthropogenic climate change has accelerated upper ocean currents in 77% of the global ocean. Specifically, increased vertical stratification due to surface warming intensifies upper ocean currents, while changes in horizontal density gradients caused by differential warming across different ocean regions results in the acceleration of surface zonal currents . There are suggestions that

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1536-515: The ocean with a fleet of automated platforms that float with the ocean currents. The information gathered will help explain the role the oceans play in the earth's climate. Ocean currents 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

1584-464: The ocean. Western boundary currents may themselves be divided into sub-tropical or low-latitude western boundary currents . Sub-tropical western boundary currents are warm, deep, narrow, and fast-flowing currents that form on the west side of ocean basins due to western intensification . They carry warm water from the tropics poleward. Examples include the Gulf Stream , the Agulhas Current , and

1632-464: The oldest waters (with a transit time of around 1000 years) upwell in the North Pacific. 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

1680-518: The same latitude North America's weather was colder. 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

1728-450: The same time, the Antarctic Circumpolar Current (ACC) is also slowing down and is expected to lose 20% of it power by the year 2050, "with widespread impacts on ocean circulation and climate". UNESCO mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for

1776-404: The subtropical gyre. The opposite is applicable when Ekman divergence is induced, leading to Ekman absorption (suction) and a subsequent, water column stretching and poleward return flow, a characteristic of sub-polar gyres. This return flow, as shown by Stommel, occurs in a meridional current, concentrated near the western boundary of an ocean basin. To balance the vorticity source induced by

1824-413: 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. Knowledge of surface ocean currents is essential in reducing costs of shipping, since traveling with them reduces fuel costs. In

1872-501: 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

1920-447: The tropics. The westerlies blow eastward at mid-latitudes. This applies a stress to the ocean surface with a curl in north and south hemispheres, causing Sverdrup transport equatorward (toward the tropics). Because of conservation of mass and of potential vorticity , that transport is balanced by a narrow, intense poleward current, which flows along the western coast, allowing the vorticity introduced by coastal friction to balance

1968-894: The viability of local fishing industries. 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 Western boundary current Boundary currents are ocean currents with dynamics determined by the presence of a coastline , and fall into two distinct categories: western boundary currents and eastern boundary currents . Eastern boundary currents are relatively shallow, broad and slow-flowing. They are found on

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2016-840: The vorticity input of the wind. The reverse effect applies to the polar gyres – the sign of the wind stress curl and the direction of the resulting currents are reversed. The principal west-side currents (such as the Gulf Stream of the North Atlantic Ocean ) are stronger than those opposite (such as the California Current of the North Pacific Ocean ). The mechanics were made clear by the American oceanographer Henry Stommel . In 1948, Stommel published his key paper in Transactions, American Geophysical Union : "The Westward Intensification of Wind-Driven Ocean Currents", in which he used

2064-476: The west at y = 0 {\displaystyle y=0} and towards the east at y = b {\displaystyle y=b} . Acting on (1) with ∂ ∂ y {\displaystyle {\frac {\partial }{\partial y}}} and on (2) with ∂ ∂ x {\displaystyle {\frac {\partial }{\partial x}}} , subtracting, and then using (3), gives If we introduce

2112-523: 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. 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

2160-553: The wind stress forcing, Stommel introduced a linear frictional term in the Sverdrup equation, functioning as the vorticity sink. This bottom ocean, frictional drag on the horizontal flow allowed Stommel to theoretically predict a closed, basin-wide circulation, while demonstrating the west-ward intensification of wind-driven gyres and its attribution to the Coriolis variation with latitude (beta effect). Walter Munk (1950) further implemented Stommel's theory of western intensification by using

2208-404: The winds that drive them, and the Coriolis effect plays a major role in their development. 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 . In addition, the areas of surface ocean currents move somewhat with

2256-401: The world. They are primarily driven by winds and by seawater density, although many other factors influence them – including the shape and configuration of the ocean basin they flow through. The two basic types of currents – surface and deep-water currents – help define the character and flow of ocean waters across the planet. Ocean currents are driven by the wind, by the gravitational pull of

2304-437: Was suggested to lead to a downward vertical velocity and therefore, a squashing of the water columns, which subsequently forces the ocean gyre to spin more slowly (via angular momentum conservation). This is accomplished via a decrease in planetary vorticity (since relative vorticity variations are not significant in large ocean circulations), a phenomenon attainable through an equatorially directed, interior flow that characterizes

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