Theory question 204
Oceans and Lakes(a) Identify and explain any four factors which determine the direction of flow of ocean current
(b) Using specific examples, discuss the effects of ocean currents on the climate of the adjacent coastal area.
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(a) Planetary (prevailing) winds drag surface water, e.g. trade winds drive the equatorial currents westward
Temperature/density differences: warm light water moves poleward at the surface, cold dense water moves towards the equator
Salinity: water of low salinity flows on the surface towards water of high salinity
Rotation of the earth (Coriolis force): currents deflected to the right in the northern hemisphere and to the left in the southern hemisphere
Shape of coastlines and relief of the sea floor divert currents
(b) Warm currents raise winter temperatures of coasts, e.g. North Atlantic Drift keeps NW Europe mild and Norwegian ports ice-free
Warm currents bring moist air and rainfall, e.g. Guinea current on the West African coast, Mozambique current on SE Africa
Cold currents lower temperatures and cause aridity/coastal deserts, e.g. Benguela (Namib desert), Canaries (western Sahara), Peruvian (Atacama)
Meeting of warm and cold currents causes fog (e.g. Newfoundland) and rich fishing grounds
Give a named current and a named coast for each effect.