Lively currents

Image of the Month - June 2000

Ocean circulation variability (root mean square of variations in dynamic topography) derived from combined observations by the Topex/Poseidon, ERS-1 and ERS-2 satellites between October 1992 and November 1998. (Credits CLS)

The world's oceans are subjected to many movements and variations. These movements are a lot "livelier" in some regions than others, chiefly in the strongest currents near the western seaboard of the oceans, such as the Gulf Stream in the North Atlantic, the Malvinas Current in the South Atlantic, the Kuroshio Current near Japan, and the Agulhas Current in the Indian Ocean, south of Madagascar. The strong variations in these zones are caused by intense eddying generated by instabilities in these powerful ocean currents. Sea level variations in the vicinity of these currents, caused by eddies tens or hundreds of kilometers across, can be as much as 30 centimeters. The Antarctic Circumpolar Current is another highly energetic current unbounded by any continent.

On the other hand, there are zones on either side of the Equator that hardly vary at all. Other intermediate zones exhibit phenomena that are more intermittent than ocean currents. The El Niño phenomenon in the Equatorial Pacific Ocean is a good example.

Satellites provide a global picture spanning several years to help us monitor these ocean variations more closely.

See also: