1. El Niño

2. What is El Niño? A shift in ocean current direction and water temperature El Niño: the ocean part: Warm phase of ENSO: El Niño - Southern Oscillation Southern Oscillation: the atmospheric part; a global wave pattern La Niña: is the cold phase of ENSO: Cool sea temperatures in tropical Pacific EN events occur about every 3-7 years

3. El Niño Effects of El Niño Normally, cold water rises up the shore of South America and brings fish food. El Nino brings warm water and the current sinks near S.A. A shortage of fish food means less fish for fishermen and the rest of the population. The warm water also brings rain to Peru. Australia has a cold current now and drought is produced.

4. Peak El Niño occurs about Christmas season... “Christ Child”“Christ Child” “The Boy”“The Boy” “The Little One”“The Little One” Cf: La NiñaCf: La Niña “The Girl”“The Girl”

6. Warm Cold Warm Cold (2) Warm water heats the atmosphere, the air rises, and low-level trade winds converge toward the warm water. Subsiding air occurs in the eastern Pacific basin. December-February Average Conditions (2) Warm water heats the atmosphere, the air rises, and low-level trade winds converge toward the warm water. Subsiding air occurs in the eastern Pacific basin. Winds and Sea Surface Temperature are COUPLED. The SSTs influence the winds and vice versa. (1) Easterly trade-winds help push warm water to the western Pacific and upwell cold water along the equator in the eastern Pacific Ocean.

7. Easterly trade winds weaken Thermocline deepens and the cold water upwelling decreases in the eastern Pacific. Convection shifts eastward over the central and/or eastern Pacific Ocean. Convection becomes suppressed over the far western Pacific/ Indonesia.

8. ENSO Impacts Occur around the world Droughts (e.g. Australia, Africa, Brazil, Indonesia) Floods (e.g. Peru, southern USA)

9. The drought of 1988: cost about $40 billion

10. Star Tribune Aug 2 1993 Minneapolis, MN FLOODS Upper Mississippi Basin Source: Trenberth

11. El Niño and Global warming 1998 warmest year on record, 2001 second warmest El Niño contributes to global warming There is a pattern of more and bigger El Niños in past 20 years El Niño years La Niña years Is global warming contributing to changes in El Niño? Likely, yes, to some extent. Which part is natural variability?