This proposal addresses the geometry and flow dynamics of three large ice caps in the Canadian arctic islands, with implications for glacier mass balance and the rate of sea-level change in a warming world. The work involves a combination of airborne 60 MHz radar to measure ice thickness, which is at present poorly known for these ice caps, and satellite remote sensing of ice velocities. Thickness and velocity data allow calculation of mass loss by iceberg production from the major outlet glaciers of these ice caps. Iceberg production is widely acknowledged as the least well known element in the mass balance of arctic glaciers, and indeed, ice masses worldwide. Internal radar-reflecting horizons and bed power-reflection coefficients also indicate glacier thermal structure. The data will be used as boundary conditions in three-dimensional numerical modelling studies of the response of these ice masses to climate change through time