EL NINO 



The name El Nino is generally identified with large-scale 

 disturbances which occur in the northern part of the Peru Current 

 in certain years ^ reported to be at intervals of about every seven 

 years. However, El Nino is believed to be a local term for a 

 current that has been observed in late December for many years. 



In December the northerly winds blowing across Central America 

 reach farther south and drive water from the Gulf of Panama southward 

 along the Peini coast. This current flows southward in a tongue-shaped 

 band 1 to 2 miles wide between 3° aii<i ^'S. The intensity of this 

 phenomenon increases considerably in some years and influences a 

 larger part of the northern nearshore portion of the Peru Current. 

 During such periods the Peru Current retards, the temperature of the 

 sinrface water rises sharply, and the southward flow comes as far as 

 20 S. This condition, most commonly referred to as El Nino, resuJLts 

 in a layer of warm water about 75 feet deep and as wide as 20 miles. 



Although the origin of this flow is not definitely known, it 

 is believed that northwesterly winds that penetrate farther south 

 than usual cause the Peru Current to weaken; close to shore a 

 south-setting flow develops as the cool Peru Current is replaced 

 by warm water with characteristics similar to those of the Pacific 

 Equatorial Counter current. Mass mortality of marine organisms 

 results when the cold and warm waters coverge. 



The southward excursion of El Nino is most prevalent in 

 January through March, when it is halted by the reappearance of 

 southeasterly trade winds and the re-establishment of upwelling 



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