Numerical Investigation of Tidal Processes and Phenomena in the Weddell Sea, Antarctica

In the framework of the BRIOS (Bremerhaven Regional Ice OceanSimulations), a three-dimensional tidal model was developed to investigate tidal processes in the southern Weddell Sea. The model is based on the free surface SCRUM (S-Coordinate Primitive Equation Ocean Model), modified to allow for the inclusion of the horizontal component of the Earth´s rotation vector, the equilibrium tide and ice shelves. Barotropic tides are simulated in a regional two-dimensional (x-y) configuration for the Atlantic Sector of the Southern Ocean. In this investigation, the semidiurnal M2 and S2 and the diurnal K1 and O1 frequencies are considered. For both semidiurnal constituents, maxima amplitudes are found in the southwestern corner of the Filchner-Ronne Ice Shelf (FRIS). Diurnal tides have higher amplitudes at the continental shelf break where they excite continental shelf waves of same period propagating in the along-slope direction. With the full three-dimensional model, baroclinic tidal currents are studied in the inner Weddell Sea, using an orthogonal curvilinear 3D grid. Semidiurnal and diurnal periods are considered, although the emphasis is on the superinertial frequencies at which free propagating internal tides can be generated at the latitude range of the inner Weddell Sea. The vertical structure of tidal currents in the southern continental shelf region and beneath FRIS are described in detail, including their seasonal variability. The model results show that tidal currents contribute significantly to the turbulent mixing at the shelf break of the southern Weddell Sea and beneath FRIS. They also suggest that tides have a direct effect on both water mass formation through mixing and on water mass modification through heat transport to the upper boundary layer, in the ice shelf cavities and by opening leads in the sea ice.