Higher Geography Ocean Currents


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A resource to support the teaching of the Scottish Higher Geography Atmosphere Unit.

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Higher Geography Ocean Currents

  1. 1. Ocean Currents Higher Geography Atmosphere
  2. 2. Introduction <ul><li>Oceanic currents play an important role in redistributing energy . They make sure that the low latitudes (equator) does not become too hot and the higher latitudes (Poles) do not become too cold. </li></ul>
  3. 3. Oceanic Circulation <ul><li>Energy is redistributed in the oceans by ocean currents, this is called oceanic circulation . </li></ul><ul><li>This huge movement of water can result in warm water being transferred towards the Poles and cool water being transferred towards the equator. </li></ul>
  4. 4. Ocean Currents <ul><li>An ocean current is any more or less permanent or continuous, directed movement of ocean water that flows in one of the Earth's oceans. </li></ul><ul><li>Ocean currents can flow for thousands of kilometres. They are very important in determining the climates of the continents, especially climate regions next to oceans. </li></ul>
  5. 5. Examples The best example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. The California Current makes the Hawaiian Islands somewhat cooler (sub-tropical) than the tropical latitudes in which they are located.
  6. 7. Gulf stream North Pacific Drift North Atlantic Drift North Equatorial East Greenland West Australian West Wind Drift Brazil Current
  7. 8. In simple terms how do ocean currents work? (1) <ul><li>Ocean currents are driven by thermohaline circulation . This is direven from thermo, for heat and haline, for salt, which together determine the density of sea water. </li></ul>
  8. 9. In simple terms how do ocean currents work? (2) <ul><li>Uneven heating of surface water in high and low latitudes sets up convection currents which transfer energy. </li></ul><ul><li>The water round the Poles is more dense than at the equator because it contains more salt. Salt does not freeze. </li></ul>
  9. 10. The Thermohaline Conveyor Surface currents (such as the Gulf Stream) head polewards from the equatorial Atlantic Ocean, This dense water then flows downhill into the deep water basins Resurfacing in the northeast Pacific Ocean 1200 years later Deep Cold Water Warm Water Deep Cold Water Shallow Warm Water Shallow
  10. 11. Winds <ul><li>Global Winds cause frictional drag on large water surfaces. </li></ul><ul><li>Ocean currents therefore tend to follow prevailing wind directions . </li></ul>
  11. 12. The Coriolis force <ul><li>The Coriolis force means that winds are deflected to the right (clockwise) in the northern hemisphere and to the left (anticlockwise) in the southern hemisphere. </li></ul><ul><li>Ocean currents are also deflected to the right (clockwise) in the northern hemisphere and to the left (anticlockwise) in the southern hemisphere. </li></ul>
  12. 13. Shape of continents <ul><li>Ocean current direction is modified by the shape of the continents . </li></ul><ul><li>Consequently the major oceanic basins have huge, roughly circular shaped loops of water called gyres . </li></ul>A good example of this is the Gyre that forms around the Ivory Coast in Western Africa.