(i) Currents affect the ocean temperature. It varies with the type of current:
• Cold Currents bring cold water into the warm water oceans for example, Labrador Current. These are found along the middle latitudes in both the hemispheres, and in higher latitudes along the east coast in Northern Hemisphere.
• Warm Currents bring warm water to the colder oceans, for example Gulf Stream. They are found in the lower and middle latitudes along the east coasts of the continents in both the hemispheres. They are also found along the west coast of the continents in higher latitudes of Northern Hemisphere.
North Western Europe is dominated by the North Atlantic drift, a warm current broken away from Gulf Stream. This brings in warm waters and raises the temperature of the coastline.
(ii) The currents are caused by:
1) Primary Forces: They influence the movement of the water, and are responsible for formation of currents, like:
• Solar Energy: The expansion of water around the equator leads to the creation of a gradient, which makes the water flow.
• Wind propels the water to move along its direction.
• Gravitational pull of the earth creates gradients for the water to flow.
• The Coriolis Force interferes the moving water and leads to the formation of Gyres.
2) Secondary Forces: These influence the way the currents move in the oceans, as they affect the vertical mobility of water, like:
• Difference in the density of water
• Difference in the salinity of water
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