Barotropic tides beneath the Amery Ice Shelf

Abstract

A barotropic tidal model has been applied to the Amery Ice Shelf cavity and Prydz Bay region of East Antarctica. The sensitivity of the tidal solution of the model to variation of the water column thickness of the Amery Ice Shelf cavity has been determined. A best estimate water column thickness grid is presented which both fits available water column thickness data (bed elevation and ice thickness) and results in reasonable agreement with available tidal elevation data. This is an important result for the Amery Ice Shelf given the severe lack of sub-ice shelf bed elevation and limited direct ice thickness measurements. Using the resulting topography, simulated tidal current speeds in the sub–Amery Ice Shelf cavity are significantly less than those beneath other major embayed Antarctic ice shelves, with maximum tidal current speeds of 26 cm s1 indicated for this cavity. Similarly, the estimated energy dissipation beneath the Amery Ice Shelf due to surface friction of 6 MW is low in comparison with the other ice shelves. Tidally induced vertical mixing is found to be too weak to destroy the stratification associated with the relatively warm water in the lower part of the cavity and ice shelf meltwater in the upper part of the cavity. However, it is proposed that buoyancy-driven upwelling, rather than vertical mixing, is sufficient to bring the lower water mass into contact with the ice shelf. The depth-averaged model suggests that barotropic tidal processes have little influence on the oceanographic properties of the Amery Ice Shelf cavity.