Ocean Current - Factors and Impact UPSC

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.