Oceanic water is never static, it remains dynamic (wave, tide, current, tsunami) to maintain the equilibrium in ocean.
Ocean Current define as general movement of water in a fairly defined direction over a great distance.
Classification of Ocean Currents :
Stream : Stream refers to surface motion which is still more defined. It's velocity is maximum.
Drift : Drift refers to slow motion of the surface layer without clear boundaries and the motion being very slow (speed - 16 to 24 Kms/day).
Current : Current refers to surface movement which is more rapid and more defined in terms of direction. The velocity of current is moderate (the speed in between 6-8 km/hr).
Two types of Ocean Current :
1. Warm Current -
* Origin - lower latitude
* Found - Eastern margin of continent
* Warm Current move from low latitudes (equator) to high latitude (pole).
2. Cold Current -
* Origin - high latitude
* Found - Western margin of continent
* Cold Current move from high latitudes (pole) to low latitudes (equator).
The main function of of Ocean Currents are distribution of Heat.
Characteristics of Ocean Currents :
* Ocean Current move fairly defined direction over a great distance.
* The heat engine of ocean are current.
* The general direction of current in Northern Hemisphere is Clockwise while in the Southern Hemisphere it is anti-Clockwise.
* The warm current move poleward and cold current move towards warm water.
* The shape and position of coast also guide the direction of current.
* Current not only flow on surface but also below at the surface.
Factors determine the Ocean Current :
1. Factors related to Nature of Earth :
* Rotation of Earth - The earth movement deflects ocean currents to the right.
* Coriolis Force - Ocean Currents move clockwise direction in Northern Hemisphere and anti-clockwise in Southern Hemisphere according to Farrell's law.
* Gravitational Force - Due to gravity, pulling and pushing of ocean water on the basis of density of water.
* Centripetal Force.
2. Factors Originating Inside the Ocean :
* Temperature - The difference in heating and surface temperature play a key role in movement of ocean water. Warm current move towards cold current and cold current move towards warm current to maintain equilibrium in temperature.
* Salinity - Higher salinity of water move towards lower salinity of water.
* Density - Ocean water move from high density of water to low density of water. It's affected by temperature and salinity of water.
* Melting ice.
3. Factors Originating out side the Ocean :
* Atmospheric Pressure - No matter in this world, Wind is always move from high pressure area to low pressure area. It's influence the ocean currents.
* Planetary Winds - 'Trade Wind' blow in between equator & tropics and 'Westerlies' blow in the temperate latitudes which influence ocean currents.
* Shape of the Coast - Continent coastal shape guide the direction of current. e.g. the tip of southern Chile divert part of the West Wind Drift northwards as the Peruvian Current.
* Evaporation and Precipitation.
Currents in the Pacific Ocean :
Warm Currents -
*North Equatorial Current
* South Equatorial Current
* Counter Equatorial Current
* Kuroshio Current
* East Australian Current
* North Pacific Current
Cold Currents -
* Oyashio Current
* California Current
* Humboldt or Peruvian Current
Currents in the Atlantic Ocean :
Warm Currents -
* North Equatorial Current
* South Equatorial Current
* Equatorial Counter Current
* Florida Current
* Brazilian Current
* Norwegian Current
Cold Currents -
* Canaries Current
* Labrador Current
* Benguela Current
* Falkland Current
* E. Greenland Current
Currents in the Indian Ocean :
Warm Currents -
* North Equatorial Current
* South Equatorial Current
* The North East Monsoon Drift
* The South West Monsoon Drift
* Mozambique Current
* Madagascar Current
* Agullhas Current
Cold Currents -
* Somali Current
* West Australian Current
Impact of Ocean Currents :
* Warm ocean currents bring rains on the east coast of continental margin and also the interior while cold ocean currents do not on west coast of continental margin.
* Cold Currents are one of the reason why deserts are located the western margins of continents in the sub-tropical regions. e.g. Namib Desert - Benguela Current (cold)
* The mixing ground of cold and warm ocean currents aids to replenish the oxygen and increase the growth of phytoplankton which is regions of excellent fishing grounds. e.g. Newfoundland - mixing ground of Labrador Current (cold) and Warm Gulf Stream (Warm).
* Warm and Cold ocean currents affects the local climate of a region.
* Navigation : The coincident of the atmospheric circulation of the winds and oceanic circulation of the currents to help in the navigation of the ship.
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