HR: 08:30h
AN: PP11C-03 INVITED     [Abstracts]
TI: El Ni¤o, Past And Future
AU: * Cane, M A
EM: virginia@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AB: Abstract I review forecasts of the future of El Ni¤o and the Southern Oscillation (ENSO), a coupled instability of the ocean-atmosphere system in the tropical Pacific with global impacts. The physics of the ENSO cycle is briefly discussed, with special attention to the Bjerknes feedback, the instability mechanism which figures prominently in ENSO past and future. Our knowledge of ENSO in the paleoclimate record has expanded rapidly within the last 5 years. The ENSO cycle is present in all relevant records, going back 130 kyr. It was systematically weaker during the early and middle Holocene, and model studies show that this results from reduced amplification of anomalies in the late summer and early fall, a consequence of the altered mean climate in response to boreal summer perihelion. Data from corals shows substantial decadal and longer variations in the strength of the ENSO cycle within the past 1000 years; it is suggested that this may be due to solar and volcanic variations in solar insolation, amplified by the Bjerknes feedback. There is some evidence that this feedback has operated in the 20th century and some model results indicate that it will hold sway in the greenhouse future, but it is very far from conclusive. The comprehensive general circulation models used for future climate projections leave us with an indeterminate picture of ENSO's future. Some predict more ENSO activity, some less, with the highly uncertain consensus forecast indicating little change.
DE: 3344 Paleoclimatology
DE: 4522 El Ni¤o
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting