Ostracode Mg/Ca Paleothermometry in the Arctic Ocean: A Calibration Study

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0223097 DwyerThe Principal Investigator will undertake core-top calibration studies to improve the applicability, accuracy, and precision of ostracode magnesium/calcium (Mg/Ca) paleothermometry to reconstruct the late Quaternary temperature history of the Arctic Ocean and adjacent seas. The existing core-top calibration is limited to adult shells of one genus, Krithe, and includes sediment core tops that are not likely to be of modern age. These factors, along with variations in the spatial and temporal abundance of adult shells of Krithe in the Arctic, contribute to diminish the accuracy, precision (1 to 20C, depending on number of shells available), and applicability of ostracode paleothermometry in the Arctic Ocean. However, studies suggest that the adult shells of other common Arctic genera may also be used for Mg/Ca paleothermometry, and, furthermore, that eldest juvenile shells display thermodependent uptake of magnesium identical to that of adult shells. If so, the combination of juvenile/adult calibrations and calibrations from multiple genera may provide the improvements necessary to more accurately and precisely quantify the temperature history of the Arctic Ocean and adjacent seas. To test this hypothesis, modern adult and juvenile shells of common Arctic genera Krithe and Cytheropteron will be analyzed from an extensive collection of existing, high-quality sediment core tops (box cores and multicores) from Arctic, Atlantic, and Pacific ocean basins at water temperatures ranging from -1 to 120C. A subset of these core tops have been used for benthic foraminifer Mg/Ca calibration studies. The research will provide for the first comprehensive calibration-comparison of the two most promising deep-sea paleothermometers available for paleoceanographic and paleoclimate studies.