Radar measurements of ice sheet thickness of outlet glaciers in Greenland

We have conducted airborne measurements over the Greenland ice sheet from the NASA P-3B aircraft using a 150-MHz coherent radar depth sounder to obtain extensive ice sheet thickness measurements. Simultaneous measurements of ice sheet elevation were also made using a laser altimeter. In outlet glacier areas along the ice sheet margin, the ice surface is characterized by a very rough, crevassed surface near the calving front. The rough ice surface generates signal clutter, which can mask the bottom echo. We are developing a technique to remove the surface clutter component from the signal to reveal the bottom echo, providing a complete ice thickness survey to the calving front of outlet glaciers. This technique makes use of a dense array of ice surface elevation measurements provided by the laser altimeter to characterize surface roughness. Surface roughness parameters are then used in a backscatter model to characterize the clutter waveform, which can be subsequently removed from the radar signal.