November 17, 2013

What are the effects of Ocean Currents?

1. Effect on Climate: The climate of the coasts become warm or cool according to the current washing the coast which may be warm or cool.
(i)         Temperature: Warm or cold ocean currents flowing near a coast exert a significant climatic influence. The warm Equatorial currents tend to raise the temperature of the places where they flow. Labrador Current remains frozen for nine months on account of the influence of the cold Arctic Current, while the British Isles enjoy a mild climate on account of the influence of the warm North Atlantic Drift. The otherwise hot climate of Peru is greatly cooled by the Peru Current. On account of the influence of the North Atlantic Drift the harbours of Norway, even beyond the North Cape are free from ice throughout the year, while Greenland in the same latitudes is ice-bound all the year round. The warm Kuroshio keeps the ports of the Alaskan coast ice-free in winters.

(ii)        Rainfall: The air above the warm ocean current becomes warm and acquires greater capacity to absorb moisture. Thus, the winds help in increasing the amount of precipitation in the affected coastal areas. For example, the North Atlantic Drift, the Kuroshio current bring in sufficient rainfall along the western coasts of Europe and eastern coasts of Japan respectively.
On the other hand, cold currents discourage rainfall. For example, Kalahari desert along the western coast of South Africa and Atacama desert along the western coast of South America owe their existence to some extent to Benguela and Peru Currents respectively.
(iii)       Fog: Dense fog occurs where the warm and cold ocean currents meet. The air above warm current is warm and acquires a lot of water vapour. When it meets the cold air above cold ocean currents, the water vapours of the warm air are condensed into minute water particles which form fog. Japanese coast has dense fog when the warm Kuroshio Current meets the cold Oyashio Current. Similarly, New Foundland where the warm Gulf stream meets the cold Labrador current creates a dense fog.
(iv)       Violent Storms: Violent storms follow the line of meeting of cold and warm currents. The hurricanes which occur off the coast of United States follow the line where Gulf Stream mingles with the cold Labrador Current.

2. Effect on Marine Organisms: The sea has innumerable microscopic organisms which are called planktons. The fish feed on planktons. Ocean currents move organic material off the coast which is the food of planktons. The more the planktons, higher the concentration of fish.

3. Effect on Commerce
(i)         On account of the influence of warm currents, harbours are kept open in winter, facilitating trade throughout the year.
For example, the coasts of UK. Norway, etc., should normally freeze in winter but due to warm ocean currents, they remain unfrozen and trade remains unfettered. In fact the warm Gulf Stream affects even such a place as Spitsbergen which is situated deep in the north. Montreal at the mouth of the St. Lawrence River remains open for the whole of the year but Vladivostok is snow bound for almost the whole of the year due to cold current along the coast.
(ii)        Sailing vessels are aided or hindered by the direction of currents. Such vessels from England, bound for Australia move towards Rio de Janeiro in order to have a favourable current across the South Atlantic and the southern ocean.
 (iii) Danger to ships is caused by the Icebergs that flow in cold currents. Due to fog, the ships are not able to locate them. Many ships have sunk on account of accidents with these icebergs. However, in modem times radar helps the ships to locate icebergs even in the darkness of dense fogs.


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