Currents

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Currents

• Surface Currents
• About 10 of the oceans water is in surface
  currents, water flowing horizontally in the
  uppermost 400 m
• Driven mostly by wind friction
• Most wind energy comes from the trade winds
  (easterlies) and westerlies

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Gyres

• Water flows clockwise around the N. Atlantic
• This results in an Ekman Spiral
• This causes a build up of water in the center of
  the ocean,
• Hill of water about 2 m higher than the rest of
  the ocean.
• This hill is maintained by wind energy, friction
  with the surrounding continents, and the coriolis
  effect.
• Geostrophic Gyres
• Gyres in balance between the pressure gradient
  and the Coriolis effect are called geostrophic
  gyres (Geoearth strophe turning), and their
  currents are called geostrophic currents.

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Currents in Gyres

• Western Boundary Currents
• Located on the gyres western end
• Ex Gulf Stream (G.S.), Kuroshio, Brazil,
  Agulhas, East Australian
• Eastern Boundary Currents
• Located on gyres Eastern Boundary Currents
• Ex Canary Current, Benguela Current, California
  current, West Australian Current, Humboldt or
  Peru current
• Transverse Currents
• These are currents that connect the E.B.C.s and
  W.B.C.s
• The N. and S. Equatorial Currents in the Talantic
  and Pacific are formed by the push of the trade
  winds.
• Countercurrents and Undercurrents
• Equitorial Currents are usually accompanied by
  countercurrents flowing on the surface in
  opposite direction of the main flow.
• Countercurrents also exist beneath surface
  currents, undercurrents, they are 100 to 200 m
  below the surface and can carry as much water as
  the surface currents.

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Upwelling

• Upwelling process by which deep, cold,
  nutrient-rich water is brought from depths to the
  surface
• Coastal Upwelling the movement of surface water
  away from a coast line causes deeper water to be
  brought up in order to replace it.
• This deeper water is colder, because it is
  farther from the sun.

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El Niño

• During an El Niño the trade winds weaken, stop
  all together, or even reverse direction.
• Causes that pile of warm water in the Western
  Pacific to slosh back along the equator until it
  hits the South America
• The presence of that warm water creates a cap on
  the water column and effectively shuts down
  upwelling.

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Thermohaline Circulation

• Thermohaline (thermotemperature, halinesalt)
  circulation is the movement of water due to its
  density
• Responsible for the majority of non-surface water
  movement in the oceans, both vertical and
  horizontal

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