HR: 08:45h
AN: PP51E-04 INVITED    [Abstracts]
TI: Permanent El Nino Conditions and Meridional Expansion of the Tropical Ocean Warm-Water Pool in the Early Pliocene: Evidence, Mechanisms and Global implications.
AU: * Fedorov, A V
EM: alexey.fedorov@yale.edu
AF: Yale University, 210 Whitney Ave, KGL Department of Geology and Geophysics, New Haven, CT 06511, United States
AU: Brierley, C
EM: christopher.brierley@yale.edu
AF: Yale University, 210 Whitney Ave, KGL Department of Geology and Geophysics, New Haven, CT 06511, United States
AU: Liu, Z
EM: Zhonghui.Liu@yale.edu
AF: Yale University, 210 Whitney Ave, KGL Department of Geology and Geophysics, New Haven, CT 06511, United States
AB: Proxy temperature records obtained during the last several years show that in the early Pliocene, approximately 3 to 5 million years ago, the tropics were characterized by a permanently warm El Nino-like state. During this time interval, and possibly before, the zonal SST gradient along the equator was significantly reduced or virtually absent. Thus far, there has been no satisfactory explanation for the climate state of the Pliocene, especially for the climate conditions in the tropics and subtropics. State-of-the-art climate models fail to reproduce a permanent El Nino, even when forced by CO2 concentrations many times larger than those estimated for the early Pliocene. Here, we summarize available evidence for a permanent El Nino state and then use available proxy temperature data from Mg/Ca and Alkenone techniques to reconstruct the latitudinal distribution of temperature in the Pacific ocean for the period of around 4Ma, exactly when the east-west temperature gradient along the equator fully collapses. Several assumptions and temperature adjustments are made to compensate for the coarseness of data. Our results indicate that a strong reduction of the meridional temperature gradient (especially from the equator to the subtropics) occurred in the Pacific ocean during the early Pliocene (in comparison with today's climate). This implies a large poleward expansion of the warm-water pool in the tropical Pacific, which may have contributed to maintaining permanent El Nino conditions. Other potential implications of the reduced meridional temperature gradient may have included a significant reduction in the strength of the Hadley cell, and changes in global precipitation and wind stress patterns.
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4922 El Nino (4522)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting