New Insights on the Age and Climate Mitigation Significance of Shelf Sea Sedimentary Organic Carbon Stores

The burial of organic carbon (OC) in coastal and continental shelf sediments contributes to the regulation of atmospheric CO2 on geological timescales and potentially mitigates present-day climate change. Major efforts are now underway to map and quantify the OC held in our continental shelf seas, including the first ever assessment of a national Exclusive Economic Zone (EEZ) sediment OC resource. However, there are fundamental requirements in the realization of a reliable accounting of this natural capital, namely to constrain the OC source(s) and, perhaps more significantly, the age of the OC itself. When these OC-rich sediments are disturbed, either by natural or (increasingly) anthropogenic pressures, there is potential for significant quantities of CO2 to be released to the water column and potentially the atmosphere In this proposal we aim to provide a unique constraint on the radiocarbon age of thermal (heated) fractions of combusted organic-rich marine sediments from the UK EEZ in order to test the hypothesis that OC reactivity in offshore sediments is driven by the source, age and fate of OC. Our research is poised to highlight the key role which radiocarbon dating must now play in national OC accounting for climate mitigation services from shelf sea environments.