Ka-Band Mapping and Measurements of Interferometric Penetration of the Greenland Ice Sheets by the GLISTIN Radar

Abstract

Measuring ice surface topography over the major ice caps of Greenland and Antarctica is crucial to quantifying and understanding the effect of climate change on the Earth's environment. Multiple sensors including radars, lidars, and optical systems have been utilized in making these measurements. To integrate data from these multiple sensors into a coherent and self-consistent history of ice cap topography requires knowledge of where vertically within the snow volume the elevation measurement corresponds. This paper examines the penetration of a Ka-band cross-track interferometric radar into the dry firn at Greenland's summit using the NASA GLISTIN Ka-band interferometric radar. GLISTIN elevation measurements are compared to NASA Wallop's Airborne Terrain Mapper lidar and kinematic GPS survey measurements to assess the amount of relative penetration with GPS-surveyed corner reflectors deployed to establish the absolute vertical positioning of the radar data. We found an interferometric penetration depth estimate of 27 $\pm$ 0.3 cm. Moreover, we compare these penetration measurements to model derived estimates of the amount of interferometric penetration and provide sensitivity analysis of the amount of penetration to various ice properties. Interferometric radar mapping systems also have the ability to make wide swath topographic measurements over a wide range of weather conditions either day or night making them ideal instruments for wide area mapping. We illustrate this aspect of interferometric radar mapping with a mosaic of 24 passes of the GLISTIN instrument of the Jakobshavn Glacier area.