The El Niño phenomenon
- El Niño und La Niña
- Fishing boats in the desert: Arica in Northern Chile
El Niño (The Christ Child) demonstrates the consequences of the close interrelationship between the ocean and the atmosphere in shaping climatic events: At irregular intervals, but always around Christmastime (hence the name), a warm oceanic current caused by a shifting of high and low-pressure zones in the southwest Pacific pushes the nutrient-rich Humboldt Current away from the west coast of South America. Warmer water that is low in nutrients and has a temperature of about 28°C pushes itself on top of the cooler current, which has a temperature of about 20°C. The absence of nutrients immediately reduces plankton production, as a result of which the fish leave for richer pastures, bringing a severe economic setback to the fishing fleets and death to many marine birds and seals.
And that's not all - the weather in the affected regions is also drastically altered: Normally, the already dry winds in this region take on only small amounts of evaporating water above the cold ocean currents. The result of this is that precipitation levels throughout these extensive regions are quite low. Indeed, the driest regions in the world are found along the coastlines parallel to these upwellings, i.e. the Atacama Desert in Chile and the Namibian Desert in Namibia.
Above the water warmed by El Niño, the layering of the atmosphere is rendered unstable by the increased evaporation, resulting in deluges and severe flooding. In a particularly bad El Niño year in 1982/83, the Galápagos island of Santa Cruz, which otherwise gets about 460 mm of precipitation a year, was flooded by at least 3,225 mm. The consequences are felt not only in Peru and Ecuador, but also in Central America and Australia, where much less precipitation falls in these years.
Although the effects of the El Niño phenomenon in 1997/98 were more serious than ever before, the phenomenon per se can be described as a natural climatic cycle recurring every three to eight years. Scientists have been able to reconstruct El Niños occurring over the last 400 years, always around Christmas time, at least some of which were as severe as the next-to-last big El Niño of 1982/83.