(a) Discuss, using specific examples, any four factors that determine the pattern of movement of ocean currents the North Pacific Ocean (b) Select any one c...

Answer Details

(a) Four factors that determine the pattern of movement of ocean currents (North Pacific Ocean)

1. Prevailing winds: the planetary winds drag surface water along, giving currents their main direction. The North-East Trades drive the North Equatorial Current westward, while the Westerlies drive the North Pacific (West Wind) Drift eastward.
2. Rotation of the earth (Coriolis force): the earth's spin deflects moving water to the right in the Northern Hemisphere, so the North Pacific currents circulate in a clockwise gyre.
3. Shape and position of the land masses (coastal configuration): continents block and deflect the currents; Asia turns the equatorial water northward as the Kuroshio (Japan) Current, and North America turns the drift southward as the California Current.
4. Differences in water temperature, salinity and density: warm, less-dense equatorial water flows towards the poles while cold, dense polar water (the Oyashio/Kamchatka Current) moves towards the Equator, helping drive the circulation.

(b) One cold current: the California Current and its effects on the adjacent coast

The California Current is a cold current flowing southward along the western coast of North America.

• It lowers the temperature of the coastland, giving cool summers on the Californian coast.
• Being cold, it chills the air above it and reduces rainfall, so the adjoining coast is dry (helping to keep the California/Baja desert arid).
• It causes advection fog and mist where the cold current meets warmer air over the land.
• Where it drives cold, nutrient-rich water upward (upwelling) it encourages plankton and rich fishing grounds off the coast.