The Walker circulation is an atmospheric circulation of air at the equatorial Pacific Ocean, responsible for creating ocean upwelling off the coasts of Peru and Ecuador. This brings nutrient-rich cold water to the surface, increasing fishing stocks. It was discovered by the English physicist Sir Gilbert Walker. Atmosphere may refer to: a celestial body atmosphere, e. ... AIR is a three-letter abbreviation with multiple meanings, as described below: The Annals of Improbable Research, a monthly magazine devoted to scientific humour All India Radio - Indias Government Radio service AIR, a popular electronica band from France. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-deplete surface water. ... Sir Gilbert Thomas Walker (1868-1958) was an English physicist and statistician of the 20th century. ...

El Niño

Main article: ENSO

The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern pacific ocean, and a low pressure system over Indonesia. When the Walker circulation weakens or reverses, an El Niño results, causing the ocean surface to be warmer than average, as upwelling of cold water occurs less or not at all. An especially strong Walker circulation causes a La Niña, resulting in cooler ocean temperatures due to increased upwelling. Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 ENSO (El Niño-Southern Oscillation) is a global coupled ocean-atmosphere phenomenon. ... The pressure gradient force is the force that is usually responsible for accelerating a parcel of air from a high atmospheric pressure region to a low pressure region, resulting in wind. ... A high, or a high pressure area, is a region where the atmospheric pressure is greatest with relation to the surrounding area. ... A low, or a low pressure area, is a region of rising atmospheric air. ... Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 El Niño and La Niña (also written in English as El Nino and La Nina) are major temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. ... El Niño is also the nickname of Sergio García. ...

A schematic diagram of the quasi-equilibrium and La Niña phase of the southern oscillation. The Walker circulation is seen at the surface as easterly trade winds which move water and air warmed by the sun towards the west. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms. The ocean is some 60 cm higher in the eastern Pacific as the result of this motion. The water and air are returned to the east. Both are now much cooler, and the air is much drier. An El Niño episode is characterised by a breakdown of this water and air cycle, resulting in relatively warm water and moist air in the eastern Pacific.

A scientific study published in May 2006 in the journal Nature indicates that the Walker circulation has been slowing in recent decades. The authors speculate that global warming is a likely causative factor in the weakening of the wind pattern. Download high resolution version (696x624, 150 KB) Quasi equilibrium and La Nina phase of SO File links The following pages link to this file: El Niño Categories: User-created public domain images ... Download high resolution version (696x624, 150 KB) Quasi equilibrium and La Nina phase of SO File links The following pages link to this file: El Niño Categories: User-created public domain images ... Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 El Niño and La Niña (also written in English as El Nino and La Nina) are major temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. ... First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ...

References

• Associated Press news story, 3 May 2006: "Global Warming Cited in Wind Shift"