Quantifying Seasonal Oceanic Temperatures and the Oxygen Isotopic Composition of Seawater Over the Last 150,000 Years

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The stable isotope geochemistry of fossil foraminifera has become an indispensable tool for reconstructing paleoceanographic and paleoclimatic fluctuations in the earth's past. Specifically, isotopic data have been used to establish glacial-interglacial cycles, infer the size of continental ice-sheets and to estimate paleoceanic temperature fluctuations. Despite the success in applying these data to paleoclimatic problems, a large portion of the potential data available for analysis remains unused. In this proposal, a strategy is outlined to access this unused information to extract new paleoclimatic and paleoceanographic information from the marine fossil record. Using the intraspecific stable isotopic variability found within populations of fossil foraminiferal shells which have been individually analyzed, it is now possible to obtain absolute seasonal sea surface temperatures (SST) for paleoceans. In addition, a procedure is proposed to determine the oxygen isotopic composition of seawater ( 18Ow) during the last glacial cycle and penultimate deglaciation. 18Ow is a critical parameter used to model the growth of continental ice sheets. Absolute determinations of SST and 18Ow during key intervals over the last 150,000 years will provide a suite of new paleoclimatic information for global change models of the last glacial cycle.