HR: 17:00h
AN: PP34A-05    [Abstracts]
TI: Irrepressible El Nino: Perspectives on ENSO and Climate Change From the Deep Past.
AU: Huber, M H
EM: huberm@purdue.edu
AF: Earth and Atmospheric Sciences, Purdue Universtiy, 397 Civil Engineering Bldg, West Lafayette, IN 47906 United States
AU: * Caballero, R
EM: rca@geosci.uchicago.edu
AF: Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Av., Chicago, IL 60615 United States
AB: The tropical thermocline is shallow enough in today's climate to permit upwelling of cold, subthermocline water on the equator. As a consequence, the tropical oceans can transport a significant amount of heat poleward; furthermore, interaction between upwelling rate, SST and surface wind stress leads to strong interannual fluctuations of equatorial SST, the phenomenon known as ENSO. This is not a necessary state of affairs, however: an alternative regime is conceivable where no upwelling, heat transport or ENSO variability occur. A transition into such a regime would clearly have major consequences for global climate. Can increased radiative forcing drive such a transition? Warm climates of the deep past provide an excellent context in which to explore this question. We present results from a suite of deep-paleoclimate simulations using NCAR's fully-coupled Climate System Model (CSM), which show not only that ENSO survives even in these warm climates, but in fact plays an even bigger global role than at present. These results are supported by comparison with annually-resolved geological proxy data for the Eocene case. Finally, we present a simple model of the equatorial Pacific which facilitates qualitative understanding of the basic physical mechanisms underpinning these results.
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting