NSFGEO-NERC: Quantifying the Modern and Glacial Ocean's Carbon Cycle Including Isotopes

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Data-constrained process-based models of the modern and glacial ocean's carbon cycle will be developed and analyzed using a novel method. The method decomposes Dissolved Inorganic Carbon (DIC = Cpre + Creg) accurately into preformed (Cpre = Csat + Cdis) and regenerated (Creg = Corg + Ccaco3) components, where Csat = Csat,phy + Csat,bio is the equilibrium saturation and Cdis = Cdis,phy + Cdis,bio the disequilibrium, each with physical and biological contributions, and Csoft and Ccaco3 are organic (soft tissue) and calcium carbonate (hard tissue) components. DIC = Cphy + Cbio can thus be separated into physical Cphy = Csat,phy + Cdis,phy and biological Cbio = Csat,bio + Cdis,bio + Csoft + Ccaco3 parts. Perturbation experiments will be used to attribute the change of each component, DIC and atmospheric CO2 to changes in individual variables (circulation, sea ice, temperature, sea level and iron fluxes). Different viable equilibrium states will be produced for the modern and glacial ocean incorporating recent innovations in ocean physics, such as different mixing parameterizations and ventilation diagnostics, and in biogeochemistry, such as variable elemental (C:P) stoichiometry, dissolved iron fluxes, sediment interactions, cycling of Pa/Th, and land carbon changes. This approach will allow quantitative, process-based understanding of glacial-interglacial changes in ocean carbon storage including uncertainty estimates. It will also elucidate the response of carbon components to circulation changes. The decomposition will be extended to carbon isotopes (d13CDIC).