Glacial-Holocene changes in bottom water temperature will be calculated by measuring changes in the rate of amino acid diagenesis (isoleucine epimerization) in radiocarbon dated, planktonic foraminifera from equatorial Atlantic, Pacific and Indian Ocean cores. The extent of epimerization in a sample is a function of the time elapsed, and the integrated thermal history, since death of the organism. By constraining the age of our samples using existing accelerator mass spectrometry (AMS) 14c dated core samples, we will obtain precise determinations of epimerization reaction rates. The temperature dependence of the reaction for individual taxa will be calibrated by laboratory heating experiments and by analysis of Holocene samples from the major ocean basins, and from marginal seas where the bottom water temperatures are elevated. The results of the study will, for the first time, provide a measurement of bottom water temperature that is independent of an analysis of the oxygen isotope record. This will contribute to an improved understanding of the 180 record, allowing us to explicitly calculate ice volume (sea level) and watermass salinity values, and to test theories calling for changes in bottom water temperature during the last glacial cycle, or for floating ice shelves in the northern and/or southern hemispheres. %%% This project will determine the change in the temperature of bottom-water in the worlds ocean from the peak of the last ice age to present. The data will be generated from the rate of amino acid diagenesis in foraminifera from sedimentary cores which have been dated by AMS carbon-14 techniques. This will be the first time glacial bottom-water temperature have been determined independently of the oxygen isotope technique, and will allow greater accuracy of the paleotemperature method. These results will be important in quantifying climatic parameters so that models of glacial climates may be refined.
