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ECCO 1 degree global WOCE Synthesis: The Method |
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E. Remy, A. Koehl, Y. Lu, P. Heimbach, B. Cornuelle, |
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D. Stammer and C. Wunsch for the ECCO Consortium. |
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A global WOCE data synthesis describing the three-dimensional |
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oceanic state in the 10-year period 1992 - 2001 now exists. |
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The synthesis results from the combination of many of the WOCE |
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data sets with a general circulation model. This combination |
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solves the complete global time-dependent ocean state estimation |
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problem, up to remaining approximations in the model and underlying |
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statistics. The MIT ocean model used represents the global ocean |
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between +/- 80 degrees with 1 degree horizontal resolution, 23 |
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vertical layers, and includes parameterizations for the surface |
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boundary layer (KPP) and eddy tracer transfers (GM). |
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At the cost of increased computational load, the estimation |
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(assimilation) method is chosen specifically so that the resulting |
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state estimate is dynamically consistent with the model equations. |
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No artificial sources or sinks are introduced by the model/data |
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combination, and the resulting time-evolution satisfies the equations |
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of motion. The combination method used is based upon the method of |
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Lagrange multipliers (adjoint method), in which the adjustable parameters |
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(controls) include the initial temperature and salinity conditions, |
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and the time-dependent surface fluxes of momentum, heat and freshwater. |
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An important test of the result is passed: adjustments in these control |
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variables are consistent with prior estimates of the expected errors in |
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the oceanographic data and the meteorological analyses |