Determining the Mean, Large-Scale Circulation of the Atlantic with the Adjoint Method

Abstract

Abstract A new model approach based on the adjoint formalism and aimed at assimilating large sets of hydrographic data is presented. The goal of the model calculations is to obtain the mean, large-scale ocean circulation together with coefficients of iso- and diapycnal mixing and air-sea heat and freshwater fluxes. The final, optimal solution is required to be consistent with the principle of geostrophy and must predict realistic distributions of temperature and salinity. The model covers the entire Atlantic and has realistic topography. Model resolution is nonuniform and ranges from 2.5° to 10° horizontally and from 60 m to 500 m in the vertical. Model velocities are initialized with geostrophic flows calculated from original hydrographic station data; initial air-sea heat fluxes and mixing coefficients are taken from the literature. Mass, heat, and salt budgets are satisfied exactly, and for given boundary conditions and model flows the model temperature and salinity distributions are calculated. Then h...