El niño

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El niño

  1. 1. mass of warm surface water moving west to east across equatorial Pacific Ocean part of larger phenomenon called El Niño – Southern Oscillation (ENSO)
  2. 2. • El Niño occurs every 3 to 8 years • Usually lasts about 1 year • Scientists do not know why pressure changes causing winds to shift • Warm water arrives at South America around Christmas – hence El Niño – for the Christ Child
  3. 3. NORMAL SITUATION OVER PACIFIC OCEAN (NON-El Niño YEAR) • Low pressure over Asia • High pressure over South America • Winds blow east to west • Shallow thermocline along South America, lots of upwelling, cold water at surface • Deeper thermocline near Asia, warm surface water piles up
  4. 4. EL NINO YEARS OVER PACIFIC OCEAN: • Pressure change = Southern Oscillation • Higher pressure over Asia • Lower pressure over South America • Winds weaken or blow west to east • Thermocline deepens along South America, little upwelling, warmer water at surface • Warm surface water sloshes back along equatorial Pacific
  5. 5. SEA SURFACE TEMPERATURE IN PACIFIC OCEAN
  6. 6. EFFECTS OF EL NINO • upwelling along Peru reduced • warm water with few nutrients rises • fisheries decline
  7. 7. EFFECTS OF EL NINO • increased precipitation over parts of South America, western and southern U.S. • can result in severe flooding • drought in Australia, Indonesia, Phillipenes • reduction in annual monsoons in India • can result in severe crop damage • severe property damage and thousands of deaths

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