HR: 1340h
AN: PP23A-1395    [Abstracts]
TI: Do Tropical SST Changes Lead High Latitude Climate Change, Or Are Our Proxies Misleading Us?
AU: * Dekens, P S
EM: dekens@.ucsc.edu
AF: University of California, Santa Cruz, Ocean Sciences Department Earth and Marine Science Building, Santa Cruz, Ca 95064 United States
AU: Ravelo, A C
EM: acr@ucsc.edu
AF: University of California, Santa Cruz, Ocean Sciences Department Earth and Marine Science Building, Santa Cruz, Ca 95064 United States
AU: Anderson, L D
EM: Linda@ucsc.edu
AF: University of California, Santa Cruz, Ocean Sciences Department Earth and Marine Science Building, Santa Cruz, Ca 95064 United States
AU: Mendoza, A J
EM: Mendoza@ucsc.edu
AF: University of California, Santa Cruz, Ocean Sciences Department Earth and Marine Science Building, Santa Cruz, Ca 95064 United States
AB: Initial reconstruction of the last glacial maximum (LGM) sea surface temperature (SST) estimates showed little to no change in the world's tropical oceans. More recently, several studies have shown that the tropics were 1 to $6\deg$C cooler during the LGM and previous ice ages. These observations, as well as the timing of the SST changes, has led some researchers to hypothesize that the tropical Pacific may have played an important role in glacial/interglacial (G/IG) climate change during the late Quaternary. Uncertainty remains about the magnitude of the SST change, the spatial pattern of the changes, and the timing of tropical SST changes relative to high latitude climate transitions. For example, in the eastern equatorial Pacific (EEP) geochemical proxy data indicate that during the LGM SST was only 1 to $2\deg$C cooler at the equator , but was 2 to $3\deg$C cooler just north of the equator and in the central equatorial Pacific compared to today. Additionally, the sites on the equator record a significantly larger lead in SST compared to ice volume than one site just north of the equator. These records have been reconstructed using different SST proxies however, leading us to question if the observed geographical differences in the magnitude and timing of SST changes during recent glacial cycles could be explained by the different uncertainties inherent in each of the proxies. The EEP is a critical region because SST in this region is sensitive to changes in upwelling, and is therefore indicative of the state of the tropical Pacific, which has known air sea feedbacks that can affect global climate. A clear picture of the timing of SST changes and ice volume is needed if we are to understand the potential role of the tropical Pacific in G/IG climate change. We have generated high resolution ($\sim$2-4 k.y.) SST records at ODP site 847 ($0\deg$12'N, $95\deg$19'W, 3346m water depth) using the U$^{k'}$$_{37}$ and Mg/Ca paleothermometers extending back 500 k.y. This site provides an excellent opportunity to compare Mg/Ca and alkenone records, as it is located above the lysocline, thereby minimizing the effect of dissolution on Mg/Ca in foraminifera, and has relatively high organic matter content. The U$^{k'}$$_{37}$ SST record shows a G/IG amplitude of $\sim$$2\deg$C through MIS 8, and a larger ($\sim$5-$6\deg$C) amplitude from MIS 9-12. SST leads ice volume changes at all glacial to interglacial transitions, but the magnitude of the lead varies. Comparing the variability in these two proxies at this site over the last ~500 k.y. will increase our understanding of the behavior of these two proxies in this region, and dramatically increase our confidence in our climatic interpretations.
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting