El Nino

El Nin̄o 

a warm seasonal surface current with lower salinity that occurs in the eastern part of the Pacific Ocean.

During the summer in the southern hemisphere, the El Nin̄o spreads along the coast of Ecuador, from the equator to 5°–7° S lat. In certain years it is stronger, and, penetrating as far south as 15° S lat., it forces the cold waters of the Peru Current away from the shore. Its thin layer of warm water prevents oxygen from entering the subsurface layers, which has a lethal effect on the plankton and fish of the extremely rich Peruvian productive region, and heavy rains cause disastrous flooding along the usually arid coast. The penetration of the warm waters southward is associated with a weakening of the trade winds and the cessation of the upwelling of cold subsurface waters in the coastal areas. The disastrous phenomenon is usually observed in late December and early January, and it was particularly severe in 1891, 1925, 1941, 1953, 1957–58, and 1972–73. In the particularly bad years, the fish (anchovies) either die or abandon the coastal waters, causing high mortality among fish-eating sea birds and a reduction in the amount of guano, which is used as an agricultural fertilizer.

REFERENCES

Polosin, A. S. Problemy El’-Nin’o. Moscow, 1975. (Contains references.)
Fairbridge, R. W. “El Nin̄o Effect.” In The Encyclopedia of Oceanography. New York, 1966.

A. S. POLOSIN