A Reduced-Gravity, Primitive Equation, Isopycnal Ocean GCM: Formulation and Simulations

A reduced gravity, primitive equation, ocean GCM with an isopycnal vertical coordinate is developed. A “buffer” layer is introduced to allow the mixed layer to detrain mass at arbitrary densities without the coordinate drift or the heat loss suffered by other isopycnal models. The diapycnal velocity is derived from the thermodynamic equation. Negative layers are removed by a heat- and mass-conserving convective adjustment scheme. The model formulation on a β plane employs an A grid and allows irregular coastlines and local grid stretching. Simulations with climatological winds and surface heat fluxes based on observed sea surface temperatures (SSTs) are presented for the Atlantic, the Pacific, and the Indian Oceans. The surface mixed layer is modeled as a constant depth layer, and salinity effects are neglected in this version. The surface heat flux parameterization used here leads to errors in model SSTs, which are reasonable in the Tropics but are higher in the western boundary current regions....