current

In earth science, flow of a body of water or air, or of heat, moving in a definite direction. Ocean currents are fast-flowing bodies of seawater moved by the wind or by variations in water density between two areas. They are partly responsible for transferring heat from the Equator to the poles and thereby evening out the global heat imbalance. There are three basic types of ocean current: drift currents are broad and slow-moving; stream currents are narrow and swift-moving; and upwelling currents bring cold, nutrient-rich water from the ocean bottom.

Stream currents include the Gulf Stream and the Japan (or Kuroshio) Current. Upwelling currents, such as the Gulf of Guinea Current and the Peru (Humboldt) Current, provide food for plankton, which in turn supports fish and sea birds. At approximate five-to-eight-year intervals, the Peru Current that runs from the Antarctic up the west coast of South America, turns warm, with heavy rain and rough seas, and has disastrous results (as in 1982–83) for Peruvian wildlife and for the anchovy industry. The phenomenon is called El Niño (Spanish ‘the Child’) because it occurs towards Christmas.