Tracer Versus Observationally-Derived Constraints on Ocean Mixing Parameters in an Adjoint-Based Data Assimilation Framework

This study investigates the possibility of using an ocean parameter and state estimation framework to improve knowledge of mixing parameters in the global ocean. Multiple sources of information about two ocean mixing parameters, the diapycnal diffusivity and the Redi coefficient, are considered. It is first established that diapycnal diffusivities derived from multiple observational data sets with a strain-based parameterization of finescale hydrographic structure can be used to ameliorate model biases in diapycnal diffusivities from the Estimating the Circulation & Climate of the Ocean (ECCO) framework and the GEOS-5 coupled Earth system model. The evidence is as follows. Adjusting ECCO-estimated and GEOS-5-calculated diapycnal diffusivity profiles toward profiles derived from Argo floats using the finescale parameterization improves agreement with independent diapycnal diffusivity profiles inferred from microstructure data. In addition, several aspects of the GEOS-5 model solution, such as mixed layer d...