Refining benthic foraminiferal Mg/Ca-temperature calibrations using core-tops from the western tropical Atlantic: Implication for paleotemperature estimation

Authors

  • Amandine A. Tisserand,

    Corresponding author
    1. Uni Research AS, Bergen, Norway and Bjerknes Centre for Climate Research
    2. Department of Earth Science, University of Bergen, Bergen, Norway
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  • Trond M. Dokken,

    1. Uni Research AS, Bergen, Norway and Bjerknes Centre for Climate Research
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  • Claire Waelbroeck,

    1. LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, Gif Sur Yvette, France
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  • Jeanne-M. Gherardi,

    1. Uni Research AS, Bergen, Norway and Bjerknes Centre for Climate Research
    2. LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, Gif Sur Yvette, France
    Current affiliation:
    1. LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, Gif Sur Yvette, France
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  • Vincent Scao,

    1. Uni Research AS, Bergen, Norway and Bjerknes Centre for Climate Research
    2. LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, Gif Sur Yvette, France
    Current affiliation:
    1. LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, Gif Sur Yvette, France
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  • Christophe Fontanier,

    1. Laboratory of Recent and Fossil Bio-Indicators, UMR CNRS 6122 LPGN, Angers University, Angers, France
    2. Laboratoire Environnements, Paléoenvironnements Océaniques et Continentaux, UMR CNRS 5805, University of Bordeaux 1, Talence, France
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  • Frans Jorissen

    1. Laboratory of Recent and Fossil Bio-Indicators, UMR CNRS 6122 LPGN, Angers University, Angers, France
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Abstract

[1] Benthic foraminiferal Mg/Ca has been shown to have great potential as a proxy for reconstructing deep water temperatures. However, the exact relationship between Mg uptake in benthic foraminifera and temperature is still ambiguous, and further exploration and refinement is much needed to reduce uncertainties associated with the method. Here, we present new core-top Mg/Ca data from benthic foraminiferal species from the lower part of the thermocline in the western tropical Atlantic (northern Brazilian margin). This area is unusual in that the changes in carbonate chemistry along the transect are very small, making it an ideal region for isolating and studying the role of temperature in the incorporation of Mg into the benthic shells. Our results show that benthic foraminiferal Mg/Ca largely reflects temperature in this area. Our data are combined with previously published data to produce new and improved Mg/Ca calibration equations for a number of benthic foraminiferal species within the Atlantic Ocean. Our study provides the first C. wuellerstorfi Mg/Ca data for the 4–6°C temperature range and indicates that C. wuellerstorfi Mg/Ca is strongly controlled by temperature. As a result, the newly established C. wuellerstorfi calibration over the entire 0–6°C temperature range is significantly improved with respect to previously published C. wuellerstorfi calibrations limited to the coldest part between 0 and 4°C. Other benthic species (Cibicidoides kullenbergi, Globocassidulina subglobosa, Uvigerina peregrina, and Oridorsalis umbonatus) have also been studied, although these results are less conclusive.