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Title: An Eddy-resolving State Estimate of the Ocean Circulation during the Subduction |
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Experiment using a North Atlantic Regional Model (ECCO). |
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Authors: |
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Geoffrey Gebbie, MIT-WHOI |
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Carl Wunsch, MIT |
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Patrick Heimbach, MIT |
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An eddy-resolving ocean state estimate during the Subduction Experiment is made |
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by bringing a 1/6 degree North Atlantic regional model into consistency with |
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data through the adjoint method. A novel aspect of this work is the search for |
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an initial eddy field and eddy-scale open boundary conditions by the use of an |
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adjoint model. The adjoint model for this region of the ocean is stable and |
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yields useful information despite concerns about the chaotic nature of an |
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eddy-resolving model. Observations employed in this study are TOPEX/POSEIDON |
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satellite altimetry and mooring data from the Subduction Experiment. When |
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rigorous, statistical consistency is found between this dataset and the model, |
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we not only have a best estimate for the ocean state, but we have also acquired |
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a best estimate for the initial eddy field, open boundary conditions, wind |
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stresses, and air-sea fluxes. This study quantifies the ability of the data to |
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constrain both the large scale circulation and the eddy scale. Individual eddy |
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trajectories can also be determined. The final state estimate is dynamically |
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consistent with the General Circulation Model. Thus, we can readily diagnose |
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subduction rates, heat and other budgets from the result in a physically |
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interpretable context. In particular, the state estimate permits improved |
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understanding of the impact of eddies on the large scale process of |
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subduction. This work is part of the ECCO Consortium effort directed at greatly |
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improved estimates of the oceanic general circulation through state estimation |
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methods. |