| Concern about future global warming has heightened interest in past greenhouse climates. These warm periods, which have punctuated Earth's history, were linked to increased atmospheric concentrations of carbon dioxide (CO2). Marine sediments play a key role in the long-term removal of CO2 from the ocean-atmosphere system, mainly as organic matter and carbonate minerals. Although both sedimentary sinks ultimately remove carbon, carbonate mineral preservation temporarily increases atmospheric CO2. Furthermore, oceanic production of organic matter plus carbonate minerals, and their burial efficiencies, are strongly influenced by diagenetic processes and the feedback of benthic recycling fluxes on water column geochemistry. Earth system models offer a powerful tool to unravel the inherent complexity of the climate system. However, existing models do not incorporate realistic descriptions of diagenetic processes and, therefore, poorly represent the biogeochemical coupling between sediments and water column. I propose to overcome this limitation by integrating an Earth system model (GEOCLIM) with an advanced diagenetic model (BRNS). The integrated modelling approach will be applied to two contrasting greenhouses: the aftermath of a Neoproterozoic Snowball event and the Mid-Cretaceous Bonarelli event. My work will highlight the role of the sedimentary carbon sink and benthic-pelagic coupling on atmospheric CO2 during these extreme climatic events. |
