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Ocean Currents

Surface Circulation

  Two types of Ocean circulation:

  Surface and Deep

  Surface currents are the horizontal movement of water in the ocean’s surface

  What causes the water in the oceans to flow?

  The friction between wind and the water’s surface creates currents

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  Gyres

  Large whirls of water within an ocean basin

  5 main gyres: North and South Pacific Gyre, North and South Atlantic Gyre, and Indian Ocean Gyre

  Gyres are caused by the Coriolis Effect

  Earth’s rotation causes currents to flow away from their original course

  In the Northern Hemisphere water flows clockwise

  In the Southern Hemisphere water flows counter-clockwise

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  Upwelling

  Winds also cause vertical water movements called upwelling

  Brings colder water from depths of 50 to 300 meters to the surface

  Water from below the surface has more nutrients and thus allows a spike in life where upwelling occurs

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  Ocean Currents and Climate

  Warm water from the equator flows to higher latitudes

  Cold water from the poles flows to lower latitudes

  Earth’s heat is more evenly distributed

  How does this flow of water affect the climate of San Francisco?

Deep Ocean Circulation

  Density Currents

  Vertical currents of ocean water that result from density differences in water masses

  An increase in density is caused by a decrease in temperature or an increase in salinity

  What are the ways that salinity increases?

  evaporation and formation of sea ice

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  Global Conveyor Belt

  Once the water becomes denser through an increase in salinity and decrease in temperature the water mass sinks

  At depths below 300 meters, wind does not create currents

  What causes the deep water masses to flow?

  pressure from the new water masses sinking and pushing on old water masses

  It takes about 1000 years for water masses to complete the entire conveyor belt