HR: 09:30h
AN: PP21A-05    [Abstracts]
TI: Oxygen Isotope and Mg/Ca Constraints on the East Pacific Equatorial Front From the LGM to the Holocene
AU: * Koutavas, A
EM: athan@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia Universtity, 61 Rt 9W, Palisades, NY 10964
AU: deMenocal, P B
EM: peter@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia Universtity, 61 Rt 9W, Palisades, NY 10964
AU: Lynch-Stieglitz, J
EM: jean@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332
AB: Ocean-atmosphere interactions in the eastern tropical Pacific produce and maintain a pronounced asymmetry in sea surface temperature (SST) distribution about the equator. The equatorial cold tongue exhibits a southerly bias with minimum SSTs centered near 2°S, while the Intertropical Convergence Zone (ITCZ) has a strong northerly bias with a mean position near 7°N. The equatorial cold tongue-ITCZ front is today a strong diagnostic of ocean-atmosphere coupling and its strength is correlated with upwelling intensity and ITCZ position. Here we provide new constraints on the variability of this front from the Last Glacial Maximum to the Holocene. Oxygen isotope and Mg/Ca ratios of the planktonic foraminifer G. ruber were measured in two cores from opposite sites of the front: V21-30 in the cold tongue (1.2°S) and V28-134 in the northern Cocos Ridge (6.9°N). Both proxies indicate an enhancement of the cross-equatorial front during deglaciation and establishment of a stronger SST gradient in the Holocene compared to the LGM. Average LGM surface cooling of 2°C is observed in the cold tongue site, and 3-3.5°C in the Cocos Ridge site. These results support the recently proposed model that latitudinal shifts of the Pacific ITCZ (southward during glacial periods) modulate the strength of tropical SST gradients on orbital timescales, and can potentially exert an important influence on the character of ENSO variability.
DE: 3309 Climatology (1620)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly