Dataset: OGCM/OCMIP-Najjar

The main objective of the proposed work is to accelerate the development of global three-dimensional  (3-D) models of the pre-industrial marine carbon cycle and its anthropogenic perturbation.  We propose  to achieve this objective through a coordinated evaluation and intercomparison of four existing models of this type in the United States.  Global observational data sets-such as those provided by the Joint Global Ocean Flux Study (JGOFS), satellite ocean color measurements (such as the Sea-viewing Wide Field of View Sensor, SeaWiFS), and historical compilations-will provide and unprecedented opportunity for model evaluation and improvement.  The proposed project will capitalize on this opportunity through the direct involvement of observationalists and data synthesists in the model evaluation process.  By intercomparing controlled and carefully designed simulations by the four models, which have profound differences in their treatment of biogeochemical and physical aspects of the marine carbon cycle, we expect to improve the models at a rate much greater than would be achieved by individual modelers working in isolation.

Three distinct evaluation/intercomparison activities will be undertaken.  First, recognizing that ocean circulation plays a key role in the marine carbon cycle, aspects of the models' circulation fields that are relevant to the marine carbon cycle will be evaluated by conducting simulations of chlorofluorocarbons, natural radiocarbon and bomb radiocarbon.  Second, simulations of the uptake of anthropogenic CO₂ will be conducted and then evaluated with observed distributions of surface pCO₂ and observationally-based estimates of marine anthropogenic inorganic carbon.  Third, the natural marine carbon cycle will be simulated using a variety of approaches, the simplest of which will be common to all of the circulation models.  These simulations will be evaluated using observed distributions of surface ocean color, phosphate, oxygen, dissolved inorganic carbon, surface pCO₂.

The above set of controlled simulations is based on a framework proposed by the Ocean Carbon-cycle Model Intercomparison Project (OCMIP), an international project initiated in 1995 by the Global Analysis, Interpretation and Modeling (GAIM) Task Force of the International Geosphere-Biosphere Program (IGBP). We are seeking support for the U.S. participation in the next phase of OCMIP, bringing to it three more modeling groups, closer collaboration with those conducting and synthesizing observations, and a more structured evaluation/intercomparison of natural carbon cycle simulations. We will coordinate with a related European effort consisting of seven individual marine carbon cycle modeling groups. Model results and data analyses will be submitted to central analysis facilities (established by OCMIP) in Europe and the U.S. for processing and posting on an Internet site accessible to all participants immediately, and soon after to the general scientific community.  We expect this interchange of model output and data syntheses on an international level to greatly accelerate the development of global 3-D marine carbon cycle models and therefore contribute to two of the major elements of the JGOFS Synthesis and Modeling Project: (1) extrapolation and prediction and (2) global and regional balances of carbon and related biologically-active substances.