Changes in atmospheric CO2 content are an important index of climate changes and are regulated by oceanic circulation and nutrient distribution. Variations in seawater biologically mediated trace elements, such as Cd, can be directly linked to the carbon cycle, and can thus provide information on past climatic variations. The Cd/Ca "nutrient-like" ratio has been used as a proxy of past ocean thermohaline circulation since it has been shown that Cd/Ca ratios can fingerprint distinct water masses. Recent studies have questioned the use of these ratios as a proxy for reconstructing past oceanic productivity, due to a potential fractionation between Cd and PO4 and/or a possible temperature effect. We propose to develop a method for measuring Cd isotope ratios in marine sediments to assess the potential of Cd isotopes as a proxy of past oceanic changes in oceanic biological productivity and/or temperature during the Quaternary.
This novel approach will be achieved by establishing a chemical separation and a measurement protocol of Cd isotopes using a MC-ICP-MS instrument combined with a double spike technique to correct for instrumental mass bias. Cd isotopic measurements will be performed on variable geological materials to evaluate the extent of natural Cd isotopic fractionation. We will then focus on marine sediments to understand the parameters controlling Cd isotope fractionation in the oceans. Time-series of Cd isotopes in selected marine sediment cores will be used to trace past oceanic circulation and biological productivity during the Quaternary and establish the potential of Cd isotopes as a paleoceanographic proxy.
This project meets the objectives of the Specific Program and the Work Program for the Marie Curie Actions, since it falls within the FP6-2003-Global-2 thematic research program, comprises scientific innovation and analytical development, and will provide the applicant both the experience and training required to develop as an independent scientist.
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