El Niño

El Niño (Spanish for " the boy, the child," here specifically: " the Christ Child ", USA: El Niño - Southern Oscillation (German: El Niño - Southern Oscillation ) ( ENSO ) ) is called the occurrence of unusual, not cyclical, changing trends in oceanographic - meteorological system of the equatorial Pacific. The name is derived from the date of occurrence, namely at Christmas time. He comes from Peruvian fishermen who get the effect due to the resulting lack of fish to sense economically.

Expiration

Go to full Christmas season, the water temperature in the Pacific Ocean off Indonesia is 28 ° C, the off the coast of Peru, however, only 24 ° C. By the trade winds, it happens Peru to the buoyancy of cool water from the depths of the ocean. This buoyancy is part of the Humboldt Current off the coast of South America. In El Niño, the cold Humboldt current is gradually weaker and comes to a halt. The surface waters off the coast of Peru heats up so much that the upper water layer is no longer mixed with the cool, nutrient-rich deep water. Therefore, it comes to the death of plankton, which leads to the collapse of entire food chains.

Normally flowing warm surface water from the Pacific Ocean off South America to the west, to Indonesia. In El Niño, this process is reversed by a shift in wind zones. Within about three months, flows through the layer of hot water from Southeast Asia to South America. This is done by the equatorial Kelvin waves. The Eastern Pacific off South America warms up while facing Australia and Indonesia drops the water temperature. The Walker circulation has now reversed.

El Niño is a natural climatic phenomenon; In recent years, stops the warm ocean layer further off the coast. Whether this is related to the anthropogenic greenhouse effect or with longer-term natural variability of the Pacific, the pivoted around at El Niño from a warm to a cold phase has not been clarified so far.

Remote effects

On three fourths of the earth's weather patterns are influenced. On the Galapagos Islands and the South American coast, there is heavy rainfall. These lead to floods along the western coast of South America. Even at the North American west coast it comes to flooding.

The rain forest in the Amazon region, however, suffers from drought. Tremendous hurricanes can occur that cause enormous damage before Mexico. In Southeast Asia and Australia, it comes by the lack of rain to bush fires and huge forest fires. While in countries like Kenya and Tanzania are more rain in East Africa, (South Africa ), it is in Zambia, Zimbabwe, Mozambique and Botswana significantly drier.

It comes at a mass mortality of fish, seabirds and coral. By heating the seawater it comes to the death of the plankton off the Peruvian coast. There is in normal years up to ten times as much fish as in other shores. In El Niño find the fish nothing left to eat and wander off. The seal colonies find no more and starve many animals food. The economic damage to the people is hard to quantify.

The high temperatures in the areas occurs on coral bleaching on the reefs that were previously spared.

Europe remains a few exceptions, such as the unusually cold winter in Europe 1941/1942, spared from the effects of El Niño remote. However, an effect on the cold and snowy winter 2010/2011 was discussed in Europe and North America.

History

Conditions for the occurrence of El Niño presented within the last 300 years at intervals of two to seven (or eight) years. However, most Niños are rather weak. There is evidence of very strong El Niño events at the beginning of the Holocene, about 10,000 years ago.

Larger El Niño events were for the years 1790-1793, 1828, 1876-1878, 1891, 1925/1926, recorded 1972/1973 and 1982/1983. In the recent past there were in the years 1983/1984 and 1997/1998 to larger events. Generally it can be due to the current warm PDO phase, a shift towards a more generally positive state of ENSO (El Niño - Southern Oscillation ) recognize.

Early period of observation

El Niño affected pre-Columbian Incas and the like have even contributed to the demise of the Moche and other Colombian and Peruvian cultures. The first real record comes from the year in 1726. Another early recording even mentioned the term El Niño in relation to climate events in 1892. It comes from Captain Camilo Carrillo from his report to the Congress of the Geographical Society of Lima, in which he said that Peruvian sailors this warm northerly current El Niño called because it arises around Christmas in time.

The phenomenon was of long-term interest, as it had an effect on the guano industry and to other industries took advantage of the biological products of the sea.

Charles Todd observed in 1893 that droughts in India and Australia occurred simultaneously with the phenomenon. The same also held Norman Lockyer established in 1904. A connection with flooding in 1895 led to the field of Pezet and Eguiguren. 1924 coined Gilbert Walker ( namesake of the Walker circulation) the term Southern Oscillation.

In most years, it is unlikely that the phenomenon has implications to Europe. However, there are years in which Europe's climate seems to be correlated with an ENSO event. To see some studies a relationship between the particularly harsh winter 1941/42, the German invasion of Russia and El Niño. This may be more langskalige cycles such as the PDO to be considered, as El Niño itself

Recent observations

The large El Niño event of 1982/83 led to a strong revival of interest by the scientific community. The time from 1990 to 1994 was very noticeable as the El Niño occurred in those years in unusually rapid succession.

About the year 1982/83 and in 1997/98 El Niño was unusually strong. The water temperature was seven degrees centigrade above the normal average temperature so that thermal energy is released into the atmosphere. In this event, the air was heated at times by up to 1.5 ° C, much in comparison to the usual warming of 0.25 ° C in the context of an El Niño. 1997/98 there were in addition to an estimated death of 16 % of the world's reef systems. Since that time, the effect of coral bleaching has become known worldwide and all regions could assign appropriate bleach spots.

In recent years, the climate phenomenon should have changed, according to Sang- Wook Yeh and co-workers: It occurs not more tongue- shaped, but horseshoe. This trend could be caused by climate change or by the naturally recurring cycles of the Pacific, may occur more in the coming decades.

Forecast opportunities and SOI metric

A recent study shows that El Niño events, especially large events could be predicted more accurately than previously thought (see also the weather forecast).

The El Niño phenomenon can be predicted by characteristic air pressure anomalies in the South Pacific. For this purpose, air pressure measurements from Tahiti and Darwin ( Australia) are evaluated. Result of this evaluation is the Southern Oscillation Index ( SOI).

A related phenomenon in the Atlantic is the North Atlantic Oscillation.

La Niña

In contrast to El Niño La Niña is an exceptionally cold flow in the equatorial Pacific, so to speak, an anti -El Niño, after the naming ( spanish little girl ) is based. Through this cold flow develops over Indonesia a particularly strong area of ​​low pressure. The trade winds blow strong and long lasting. As a result, the eastern Pacific cools further and there is a lot of rain in Indonesia especially. In contrast, it is very dry in Peru and it is hardly rain.