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

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).

Previous decompositions of the ocean's carbon cycle were incomplete and plagued by the use of simplifications such as the AOU-based approximation of Csoft that can lead to large errors. The accurate and comprehensive method proposed here has the potential to set a new, transformative standard for ocean carbon cycle analysis and aid future interpretations of ocean carbon models. Significant results will be disseminated through peer-reviewed publications and presentations at scientific conferences. Results of potential interest to the greater public will be disseminated to the press by working with our institution's press offices. The continuing development of computational tools such as the Transport Matrix Method and the Model of Ocean Biogeochemistry and Isotopes will benefit the scientific community. Both are freely available through an open source distribution site and used by a large international and interdisciplinary community. This project will support training of a graduate student in oceanography, ocean biogeochemical and physical modeling. The student will have the opportunity to gain teaching experience at Oregon State University. In partnership with OSU's Science & Math Investigative Learning Experiences (SMILE) program the project will support more than 25 afterschool Science Technology Engineering and Mathematics (STEM) clubs in rural Oregon middle and high schools designed to facilitate the pathway for underrepresented students towards higher education and careers in STEM fields. Specifically, we will work with the teachers to develop and implement an ocean carbon cycle and climate science curriculum into their program. This will foster diversity and climate literacy by advance STEM education for communities that need it most.