Velocities and flux of the Filchner ice shelf and its tributaries determined from speckle tracking interferometry

Velocities of the Filchner Ice Shelf and its tributary glaciers are derived using a variation of satellite radar interferometry known as speckle tracking. The method requires a coherent pair of SAR passes, a digital elevation model and, for floating ice, an estimate of the height if difference due to the tide. Speckle tracking interferometry has the advantage that ice speed and direction can be estimated from one interferometric pair and, with adequate coherence, it is suitable for areas of high velocity and long repeat cycles. Fluxes are estimated using the ice velocities together with ice thickness data derived from a hydrostatic equilibrium model. They are given for gates downstream from the grounding lines of the input tributary glaciers, and for a gate close to the ice shelf edge. The calculations show that the flux close to the edge of the Filchner Ice Shelf (similar to 75.3 km(3)/a) is comparable to that estimated further upstream. However the errors in the estimates (similar to 10 km(3)/a) preclude any firm conclusions concerning equilibrium of the ice shelf or bottom surface melt or accretion. Assuming the upstream fluxes reflect the flow across the grounding lines, then the Recovery Glacier is the largest contributor to the ice shelf with 48% and the Slessor Glacier is the second largest with 33%. Support Force Glacier and Foundation Ice Stream both contribute similar to7%. Ice Shelf accumulation accounts for the remaining 5%.