Modeling tidal currents beneath Filchner-Ronne Ice Shelf and on the adjacent continental shelf: their effect on mixing and transport

A depth-averaged tidal model has been applied to the southern Weddell Sea. The model domain covers the southern continental shelf, including the ocean cavity beneath Filchner-Ronne Ice Shelf. Reasonable agreement with the available current meter data has been achieved. Our results confirm that in areas with shallow water and large topographic gradients, tidal oscillations with peak velocities up to 1 m s(-1) play a significant role in the vertical mixing and transport of water masses. The estimated energy dissipation beneath Filchner-Ronne Ice Shelf due to surface friction is 25 GW, approximately 1% of the world's total tidal dissipation. Tidally induced Lagrangian residual currents converging at the ice front, an area of strong mixing, draw together water masses from the continental shelf and sub-ice shelf cavity. The model indicates that Lagrangian residual currents have fluxes of up to 250,000 m(3) s(-1), and speeds of over 5 cm s(-1) along the ice front, with over 350,000 m(3) s(-1) being exchanged between the sub-ice shelf cavity and adjacent continental shelf. These currents are particularly efficient in ventilating the sub-ice shelf cavity within 150 km of Ronne Ice Front. Such strong tidal mixing will significantly modify the properties of water masses that flow through this region, particularly to the west of Berkner Island. The model predictions indicate that tidal processes strongly influence the oceanographic conditions in the vicinity of Ronne Ice Front. Shipborne observations along the ice front support many of the model predictions concerning the effect of tides on the hydrography.