SCrIPT SIGNED

Project "SCrIPT" data sheet

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 Project objective

The overall concept of this proposal is to investigate the main biogeochemical processes modulating spatial and temporal changes in marine export productivity, and assess their role in regulating atmospheric carbon dioxide (CO2) concentrations, both under present conditions and in the geological past. The exchange of CO2 between the atmosphere and ocean interior mediated by the oceanic ecosystem is a pivotal mechanism modulating the global carbon cycle, and thus, a substantial driver of the Earth’s climatic evolution.

The overarching objective of this research proposal is to develop a novel proxy to trace changes in the global strength of the marine biological carbon pump (BCP) based on stable Chromium (Cr) isotopes. Despite its significance for the global carbon cycle, the BCP is still poorly constrained. This project will explore a tracer that has recently been developed to investigate the rise of atmospheric oxygen in the early history of the Earth and develop it thoroughly through a comprehensive, multidisciplinary calibration program and apply it to the much more subtle redox variations associated with organic matter remineralization in the ocean. The proposed approach includes phytoplankton culture experiments, water-column investigations and sedimentary analysis and will aim at elucidating the mechanisms governing the reduction of Cr and its associated isotopic fractionation. The proxy will subsequently be used to reconstruct export production variability in the past and assess its role in modulating glacial/interglacial climate oscillations. These past changes tended to be much slower than the current, anthropogenic change. Nonetheless, they can help to appraise sensitivities and point toward potentially dominant mechanisms of change. The observations gathered within the framework of this research program will enable refining the evolution of the marine carbon cycle and the rapidly declining buffering capacity of the ocean.