Humboldt Current
Humboldt Current
The Humboldt Current (or Peru Current) is a system of sea flows along the western coast of South America, from latitude 42 degrees south to 45 degrees south. Cold surface waters—57 degrees Fahrenheit (14 degrees Centigrade) in Talcahuano, Chile; 63 degrees Fahrenheit (17 degrees Centigrade) in Valparaiso, Chile; 64 degrees Fahrenheit (18 degrees Centigrade) in Arica, Chile; 63 degrees (17 degrees Centigrade) in San Juan; Puerto Rico; 64 degrees Fahrenheit (18 degrees Centigrade) in Callao, Peru; 66 degrees Fahrenheit (19 degrees Centigrade) in Puerto Etén, Peru; and 68 degrees Fahrenheit (20 degrees Centigrade) at Punta Pariñas, Peru—sustain a marine ecosystem characterized by high primary productivity (>300 gC/m2-yr), and one of the largest biomasses on Earth (400 million metric tons per year). About 20 percent of the world's catches are extracted from the Humboldt Current.
The surfacing of cold water and its equatorward flow (at an average speed of 10 knots [11.5 miles, 18.5 kilometers) per hour is caused by wind shear against the coast. In addition, several upwelling centers caused by rises of the ocean floor and coastal inflections at Lachay and San Gallán-San Juanin Peru, and at Iquique, Caldera, Punta Lavapié, in Chile, reinforce the cold conditions of the sea. Under the surface water, a north-south directed flow of high salinity and nutrient content, the Gunther Current, maintains the ocean mass balance of the eastern Pacific basin. At Punta Pariñas (4.5 degrees south latitude), the Humboldt Current veers westward in the direction of the Galapagos Islands. Cooler than normal sea surface temperatures allow the existence of penguins and seals on these equatorial islands. The Humboldt Cuttent reaches as far as 120 degrees west longitude, where the surface water temperatures begin to rise above 75 degrees Fahrenheit (24 degrees Centigrade). This warmer westward flow is called the South Equatorial Current.
During particular years, when the winds in the eastern Pacific are weak and the upwelling centers lose strength, warm equatorial waters seep—by means of Kelvin waves—from the western Pacific into the eastern Pacific and temporarily overlap the cooler waters of the Humboldt Current. These warm water invasions, known as El Niño events, usually develop during the southern summer (which occurs during the change of calendar years). El Niños occurred in 2006–2007, 1997–1999, 1992–1994, 1982–1983, 1972–1973, and 1957–1958. The larger of these events are accompanied by worldwide climate anomalies, as happened in 1940–1941, 1925–1926, 1911–1912, and 1891. El Niño events dating back to 12,000 years before the present have been detected with the help of geological and archaeological techniques. Some geophysicists postulate that El Niño may have started 50,000 years ago.
After a warm El Niño episode, the return to normal conditions in the eastern Pacific basin occurs frequently through a brisk change to abnormal cold ocean conditions known as La Niña (or Anti-Niño in Spanish). At that time, the biosystems of the Humboldt Current, which are severely stressed during El Niño events, slowly return to normality. This applies particularly to the swarms of anchovies, pilchard, and jack mackerel that are reduced considerably during the warm waters of El Niño and to the sea lions, seals, and coastal birds (cormorans, pelicans, and penguins) that feed on them.
See alsoEl Niño; Fishing Industry.
BIBLIOGRAPHY
Arntz, Wolf, and Eberhard Fahrbach. El Niño: Experimento Climático de la Naturaleza. Mexico: Fondo de Cultura Económica, 1996.
Caviedes, César N. El Niño in History: Storming through the Ages. Gainesville, FL: University Presses of Florida, 2001.
Pauly, Daniel, P. Muck, J. Mendo, and I. Tsukayama, eds. The Peruvian Upwelling Ecosystem: Dynamics and Interactions. Manila, Philippines: International Center for Living Aquatic Resources Management, 1989.
CÉsar N. Caviedes