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