DR Ambedkar IAS Academy

Ocean Current

Ocean Current

  • Depending upon their temperature, ocean currents can be classified into warm currents and cold currents.
  • Warm currents flow from equatorial regions towards the polar regions and hence have a higher surface temperature. [from lower latitudes to higher latitudes]. These currents flow in the clockwise direction in the northern hemisphere and the anti-clockwise direction in the southern hemisphere.
  • Cold currents flow from polar regions towards the equator and have a lower surface temperature [ from higher latitudes to lower latitudes]. They flow in the anti-clockwise direction in the northern hemisphere and the clockwise direction in the southern hemisphere.

Factors responsible for Ocean Currents

  • The following are the factors responsible for ocean currents:
    • The Planetary winds,
    • Temperatures,
    • Salinity,
    • The earth s rotation,
    • Obstruction from land
    • The Planetary winds
  • The general distribution of winds in the lower atmosphere is called Planetary winds. The Earth’s atmosphere is divided into permanent pressure belts – The Equatorial low-pressure belt, The Sub-tropical high-pressure belt, Sub-polar low-pressure belt and Polar high-pressure belts. The planetary winds are permanent winds that blow from one pressure belt to the other. Accordingly, they have been divided into – Tradewinds, Westerlies and Polar Easterlies.
  • The Planetary winds are probably the dominant influence on the flow of ocean currents. The strongest evidence of prevailing winds on the flow of ocean currents can be witnessed in the North Indian Ocean where there is a change in the direction of ocean currents with a change in direction of the monsoon winds. The oceanic circulation pattern roughly corresponds to the earth s atmospheric circulation pattern.

Temperature

  • The differential heating of the Sun at the equator and the poles causes a difference in the temperature of ocean water. At the equator, since the temperature is higher the ocean water gets heated up and expands. This makes the warm water lighter and hence rises while at the poles, cold water is denser and sinks. Warm water from the equator slowly moves along the surface towards the poles, while the cold water from the poles slowly creeps along the bottom of the sea towards the equator.
  • Hence, the difference in heating and surface temperatures play a key role in the movements of ocean water.

Salinity

  • The density of water also depends on its salinity and the salinity of water varies from place to place. Waters of low salinity flow on the surface of waters of high salinity while waters of high salinity flow at the bottom.

The earth’s rotation and Coriolis force

  • The earth’s rotation deflects moving objects to the right and ocean currents are no exception. Under the action of Coriolis force, the movement of ocean currents in the northern hemisphere is clockwise and in the southern hemisphere, it is in the anti-clockwise direction. Hence it can be said that ocean currents obey Ferrel’s law.

Obstruction due to land

  • A landmass obstructs the direction of flow of ocean current and divides the ocean current which in turns flow in a different direction. Example: The south equatorial current in the Atlantic Ocean is obstructed by the South American continent and the South equatorial current divides to create the Brazilian current which flows in the south Atlantic Ocean.
  • Currents in the Pacific Ocean
    • North Equatorial Current (Warm)
    • South Equatorial Current (Warm)
    • Counter Equatorial Current (Warm)
    • Kuroshio System (Warm)
    • Oyashio Current (Cold)
    • California Current (Cold)
    • Peruvian or Humboldt Current (Cold)
    • East Australia Current (Warm)
    • North Pacific Drift (Warm)
  • Currents in the Atlantic Ocean
    • North Equatorial Current (warm)
    • South Equatorial Current (warm)
    • Equatorial Counter Current
    • Gulf Stream (warm)
    • Florida Current (Warm)
    • Canaries Current (Cold)
    • Labrador Current (Cold)
    • Brazilian Current (Warm)
    • Falkland Current (Cold)
    • South Atlantic Drift (Cold)
    • Benguela Current (Cold)
  • Currents in the Indian Ocean
    • The North-East Monsoon Drift
    • The South West Monsoon Drift
    • North Equatorial Current (Warm)
    • South Equatorial Current (Warm)
    • Somali Current (Cold)
    • Mozambique Current (Warm)
    • Madagascar Current (Warm)
    • Agulhas Current (Warm)
    • West Australian Current (Cold)

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