A global inventory of shelf sea carbon

The ocean is known to be a vast and globally important carbon sink and there is an urgent need to better understand the role played by shelf sea sediments in the ocean carbon cycle. Organic carbon is preferentially stored in marine muds, the deposition of which has predominantly been dictated by bottom currents controlled by waves and tides. Through numerical modelling to predict carbon accumulation, alongside data mining and synthesis, we aim to make a first-order approximation of global carbon stocks in shelf sea sediments. We are developing new high resolution numerical models to simulate the timing and distribution of carbon-rich mud accumulations across global shelf seas. These models will reconstruct current flows near the seabed driven by the tides and waves, for the period since the Last Glacial Maximum (approximately 22,000 years ago). We incorporate dynamic palaeo-topographies from the latest regional glacial isostatic adjustment models, as well as adopting the novel approach of palaeo-wave modelling (forced by palaeo-wind datasets). The simulated hydrodynamics will be used to estimate where accumulation of fine sediments may occur on shelf seas. These synthetic maps of fine sediment deposits will be constrained and validated using observational data from sediment samples (e.g., data on sediment grain size and carbon content). Radiocarbon age-constrained samples from shelf sea sediment cores will then be used to test the validity of the model predictions for estimating accumulations of carbon-rich sediments over thousands of years. As this work considers potential mud accumulation – and carbon stocks - within muddy basin fills, it builds upon existing works which to date have primarily focused on surface sediment. This novel global inventory of shelf sea carbon stocks will inform global carbon budgets and protection- and restoration efforts of these globally significant blue carbon stocks.