08 - El Nio Nio what is it? what effects does it have? why...

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Unformatted text preview: El Nio Nio what is it? what effects does it have? why should we care? What is El Nio? Ni El Nio is an oscillation of the ocean-atmosphere Ni oceansystem in the tropical Pacific Also called the "Southern Oscillation" or ENSO Oscillation" (El Nio Southern Oscillation) Ni Has MAJOR consequences for weather around the globe Normally.... Surface winds (trade winds) blow from E to W across the tropical Pacific NonEl Nio: business as usual on Ni Surface current results in zone of upwelling (cold, deep, nutrient-rich waters) along the west coast of nutrientAmericas (Pacific thermocline rises towards the east) monsoon season to Asia, Australia Warm water in western Pacific brings annual Typical seasonal weather patterns world-wide result worldfrom this configuration During An El Nio year... When an El Nio Southern Oscillation develops, an Ni the trade winds diminish and then reverse water along the equator An El Nio year This leads to an eastward movement of warm The surface waters of the central and eastern Pacific become warmer, and storms over land may increase Weather patterns change globally 1 Business as usual upwelling El Nio A nonEl Nio year Pacific sea surface temperatures (May 1988) red=warm; blue=cold El Nio year (May 1992) Pacific sea surface temperatures red=warm; blue=cold Business as usual El Nio NonEl Nio year vertical section through the equatorial Pacific (January 1997) shows warmer water to the west and cooler water to the east El Nio year vertical section through the equatorial Pacific (November 1997) shows warmer water spreading toward the east El Nio and La Nia Are Exceptions Ni Ni to Normal Wind and Current Flow Normal El Nio A Non-El Nio Year An El Nio Year In an El Nio year, when the Southern Oscillation develops, the trade winds diminish and then reverse, Ni leading to an eastward movement of warm water along the equator. The surface waters of the central and eastern Pacific become warmer, and storms over land may increase. increase. In a non-El Nio year, normally the air and surface water flow westward, the thermocline rises, and non- Ni upwelling of cold water occurs along the west coast of Central and South America. and Surface temperatures for southern California in January of the normal year of 1982 (left) and in the same month of an El Nino year (1983, right) 2 Normal to El Nio changes in temperature, Ni plankton, & dissolved nutrients Since bad El Nio of 1982-83... Ni 1982- 83... Extensive research on prediction / monitoring Historical and geological records Global awareness / preparedness for next one Peruvian fisheries decline or collapse during El Nio years. Small drifting animals and plantlike organisms called plankton form the base of the food chain on which commercial fish depend. When the normal northward flow of the cold Peru Current is interrupted, nutrient upwelling fails, plankton cannot prosper, and fish starve. http://www.pmel.noaa.gov/tao/proj_over/map_array.html 3 Historical record of El Nio events Ni El Nio La Nia (aka "Business as usual") "Business as usual" aka La Nia Characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Nio Current El Nio / La Nia conditions Ni Ni 4 ...
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