Influence of Horizontal Nonuniformity of Stratification on Internal Tides and Their Induced Diapycnal Diffusion in the Ice-Free Kara Sea

Abstract—The 3D finite-element hydrostatic model QUODDY-4 is used to study the influence of horizontally nonuniform stratification on internal tides and their induced diapycnal diffusion in the ice-free Kara Sea. This model was used to perform two numerical experiments. In the first stratification is assumed to be horizontally uniform and determined by predicted seawater temperature and salinity values found during solution of the problem. It is shown that when horizontally uniform stratification is replaced by horizontally nonuniform stratification, the amplitudes of internal tides over a bottom uplift are increased, while the amplitudes of baroclinic tidal velocities are decreased. These decreasing amplitudes of baroclinic tidal velocities instead of their increasing values typical for waves studied in a linear approximation are apparently related to wave disintegration (in the region of the critical latitude) into trains of nonlinear short-period internal waves. A similar situation arises with baroclinic tidal energy dissipation: it is either enhanced or attenuated depending on location in the sea. These changes in dissipation and stratification lead to variations in diapycnal diffusion, followed by initiation of tidal changes in the climate of the considered marine system.