ENSO: El Ni

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ENSOEl Niño Southern Oscillation

• Background, Dynamics,
• Regional Impacts,
• and Future Outlook

Josh Gellers Luis Poza EESC W4400
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ENSOBackground Information

• Coupled ocean-atmosphere instability in the
  equatorial Pacific
• Two distinct phases, El Nino and La Nina,
  occurring every 2-10 years
• Sir Gilbert Walker recognized teleconnections in
  1920s (i.e. sea-level pressure differences)
• Name coined by Peruvian fishermen
• Paleoclimate record indicates impacts as far back
  as 130,000 years ago

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ENSO Dynamics

• Normally, temperature gradient between western
  and eastern equatorial Pacific due to equatorial
  upwelling and presence of easterlies.

• During El Nino, Walker Cell is disrupted, meaning
  more convection over eastern Pacific.

• Easterly winds weaken or reverse and the eastern
  Pacific experiences a warm SST anomaly.

• During El Nino, thermocline deepens in east and
  shoals in west.

• Leading to

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ENSO Regional Impacts
El Niño Increased likelihood of -Above normal
rainfall anomaly in Peru, Ecuador, Western
US -Depleted fishery stocks in eastern Pacific
-Drought in northeast Brazil, eastern Australia,
Indonesia and southeast Asia, southeastern Africa
-Weakened Indian monsoon
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ENSO The Future

• Effects of warming and GHG increase uncertain

-ENSO neutral state more like current La Niña
-More frequent and intense El Niño events
-No change at all?