Boundary current

western boundary currentwestern intensificationEastern boundary currentwestern boundary currents1948 theory of the westward intensification of wind-driven ocean currentsocean dynamics
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.wikipedia
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Canary Current

Canaries CurrentCanariasCanary (or Canarian) Current
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 Current, and the California Current.
This eastern boundary current branches south from the North Atlantic Current and flows southwest about as far as Senegal where it turns west and later joins the Atlantic North Equatorial Current.

Humboldt Current

HumboldtPeruHumboldt ocean current
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 Current, and the California Current.
It is an eastern boundary current flowing in the direction of the equator, and extends 500-1000 km offshore.

Agulhas Current

Agulhas eddiesAgulhasAgulhas Leakage/Rings
Examples include the Gulf Stream, the Agulhas Current, and the Kuroshio.
The Agulhas Current is the western boundary current of the southwest Indian Ocean.

California Current

CaliforniaCalifornia Current Systemarea of low sea surface temperatures
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 Current, and the California Current. It is because of western intensification that the currents on the western boundary of a basin (such as the Gulf Stream, a current on the western side of the Atlantic Ocean) are stronger than those on the eastern boundary (such as the California Current, on the eastern side of the Pacific Ocean).
It is considered an Eastern boundary current due to the influence of the North American coastline on its course.

Gulf Stream

Atlantic Gulf StreamGolf StreamGulf-stream
Examples include the Gulf Stream, the Agulhas Current, and the Kuroshio. It is because of western intensification that the currents on the western boundary of a basin (such as the Gulf Stream, a current on the western side of the Atlantic Ocean) are stronger than those on the eastern boundary (such as the California Current, on the eastern side of the Pacific Ocean).
The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America.

Kuroshio Current

KuroshioTsushima CurrentJapan Current
Examples include the Gulf Stream, the Agulhas Current, and the Kuroshio.
Like the Gulf stream, it is a strong western boundary current.

Ocean current

currentscurrentocean currents
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.
These western boundary currents (of which the Gulf Stream is an example) are a consequence of the rotation of the Earth.

Westerlies

westerly windswesterlyprevailing westerly winds
The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes.
The process of western intensification causes currents on the western boundary of an ocean basin to be stronger than those on the eastern boundary of an ocean.

Coriolis force

Coriolis effectCoriolisCoriolis acceleration
In this simple, modeling setting, the principal factors that were accounted for influencing the oceanic circulation were surface wind stress, bottom friction, a variable surface height leading to horizontal pressure gradients, and finally, the Coriolis effect.
The Coriolis effect strongly affects the large-scale oceanic and atmospheric circulation, leading to the formation of robust features like jet streams and western boundary currents.

Henry Stommel

Stommel, HenryHenry M. StommelHenry Melson Stommel
Western intensification was first explained by the American oceanographer Henry Stommel.
Henry Stommel showed that the north-south gradient of the strength of the horizontal Coriolis force (the "beta effect") was responsible for the observed fact that the return flow of the slow interior gyre circulations is concentrated in fast moving western boundary currents, such as the Gulf Stream and the Kuroshio Current, a process known as western intensification.

Ocean gyre

gyreOceanic gyresoceanic gyre
This flow is returned towards the pole in an intensified western boundary current.

Sverdrup balance

Sverdrup transportSverdrup1947 theory relating the curl of the wind stress to meridional transport
The resulting Sverdrup transport is equatorward in both cases.
In 1948 Henry Stommel proposed a circulation for the entire ocean depth by starting with the same equations as Sverdrup but adding bottom friction, and showed that the variation in Coriolis parameter with latitude results in a narrow western boundary current in ocean basins.

Coast

coastalcoastlineseaboard
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.

Benguela Current

BenguelaBenguela NiñoBenguela Upwelling
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 Current, and the California Current.

Upwelling

coastal upwellingupwelledupwell
Coastal upwelling often brings nutrient-rich water into eastern boundary current regions, making them productive areas of the ocean.

Oceanic basin

ocean basinbasinbasins
They are found on the eastern side of oceanic basins (adjacent to the western coasts of continents).

Trade winds

trade windtradewindseasterlies
The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes.

Stress (mechanics)

stressstressestensile stress
This wind pattern applies a stress to the subtropical ocean surface with negative curl in the northern hemisphere and a positive curl in the southern hemisphere.

Curl (mathematics)

curlcurl operatorcross product of a curl
This wind pattern applies a stress to the subtropical ocean surface with negative curl in the northern hemisphere and a positive curl in the southern hemisphere.

Potential vorticity

Potential vorticity unitpotential-vorticityPV
Because of conservation of mass and potential vorticity conservation, that transport is balanced by a narrow, intense poleward current, which flows along the western boundary of the ocean basin, allowing the vorticity introduced by coastal friction to balance the vorticity input of the wind.

Vorticity

vortex dynamicsvortex lineVORTEX LINES
Because of conservation of mass and potential vorticity conservation, that transport is balanced by a narrow, intense poleward current, which flows along the western boundary of the ocean basin, allowing the vorticity introduced by coastal friction to balance the vorticity input of the wind.

Atlantic Ocean

AtlanticNorth AtlanticNorth Atlantic Ocean
It is because of western intensification that the currents on the western boundary of a basin (such as the Gulf Stream, a current on the western side of the Atlantic Ocean) are stronger than those on the eastern boundary (such as the California Current, on the eastern side of the Pacific Ocean).

Pacific Ocean

PacificSouth PacificWestern Pacific
It is because of western intensification that the currents on the western boundary of a basin (such as the Gulf Stream, a current on the western side of the Atlantic Ocean) are stronger than those on the eastern boundary (such as the California Current, on the eastern side of the Pacific Ocean).

Eos (newspaper)

EosEOS magazineEOS Transactions
In 1948, Henry Stommel published a paper in Transactions, American Geophysical Union titled "The Westward Intensification of Wind-Driven Ocean Currents", in which he used 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.

Stream function

streamfunctionLagrange stream function
:If we introduce a Stream function \psi and linearize by assuming that D>>h, equation (4) reduces to