Movements of masses of water in the ocean

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• Movements of masses of water in the ocean

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Formation of Surface Currents

• The forces that move water to produce ocean
  currents are caused by
• Rotation of the earth
• Winds
• Water density Differences

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Effect of a Rotating Earth

• Turns from west to east.
• Velocity of rotation at its surface is greatest
  at the equator and least at the poles.
• This is called the Coriolis effect.

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Gyres circular flow of water

• Clockwise in the northern hemisphere
• Counterclockwise in the southern hemisphere
• 5 Major Gyres
• North Atlantic
• South Atlantic
• South Pacific
• North Pacific
• Indian

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Ekman Transport

• Coriolis effect spinning of the earth
• Water flows to the right of the direction of the
  wind
• Water in each water column flows a little more to
  the right as you go down
• A down flowing spiral occurs

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Western and EasternBoundary Currents

• 5 major ocean gyres flow in relation to the spin
  of the earth geostrophic currents.
• Currents on the western boundary of the ocean
  flow from the equator to the poles
• Currents on the eastern boundary of the ocean
  flow from the poles to the equator
• Western boundary currents are narrower, faster
  and deeper than other currents.

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Countercurrents and Undercurrents

• Countercurrent - water at the equator where lack
  of wind allows them to flow in the opposite
  direction of the current next to it.
• Undercurrent water flows beneath and opposite
  of the current over it.
• Both return excess water to their source

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Upwellings and Downwellings

• Upwellings
• Form when winds parallel to shore force water
  away from shore west coast of continents.
• Water from the bottom is brought up to replace
  the moved water
• Water brings with it nutrients from the ocean
  bottom
• Downwellings
• Form when winds parallel to shore force water
  into shore east coast of continents
• Extra water is forced down towards the bottom

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Heat transport and Climate

• Currents redistribute heat throughout the globe
• Without these, Earth would have more extreme
  weather.
• Cold water from the poles keeps the Galapogos
  Islands cool even though they are in the tropics
• Warm water from Gulf Stream, warms the air above
  and keeps much of Europe warmer than other places
  at similar latitudes.

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El Nino Southern Oscillation (ENSO)and La Nina

• ENSO is a reoccurring natural phenomenon in which
  the Eastern Pacific is warmer than usual causing
  global weather changes.
• Upwellings in California and Peru decrease or
  stop
• Increases Pacific tropical cyclone activity
• Occurs every 3-8 years
• La Nina is a intense return to the normal
  conditions following strong ENSO
• Colder than normal conditions in California and
  Peru

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