A radar suite for ice sheet accumulation measurements and near-surface internal layer mapping

Many satellite, airborne, and in situ observations have been made to better understand the mass balance of the ice sheets. Satellite missions such as GRACE, ICESat, and Cryosat provide broad coverage, but are only capable of collecting data at relatively coarse temporal and spatial resolutions. Satellite observations alone are not sufficient to fully understand all mechanisms responsible for changes in the overall ice sheet mass balance. While these are sufficient over much of the interior of the ice sheet, to understand and model the dynamics of fast flowing glaciers and the margins of the ice sheet, finer resolution data are required. Airborne platforms, especially autonomous platforms, allow for key regions of the ice sheets to be measured with fine-resolution remote sensing instruments. These platforms provide more accurate ice thickness estimates, internal layer mapping, and ice-bedrock interface imaging. To address this gap in the observations, we are designing and developing an instrumentation suite to be deployed on crewed and uncrewed aircrafts. Here we will focus on two radars in the instrumentation suite: an accumulation radar and a radar altimeter. The altimeter will be capable of measuring surface elevation and near-surface internal layers to a depth of about 10 m. The accumulation radar will be capable of measuring internal layers to a depth of about 100 m. A previously developed 150 MHz radar depth sounder/imager will be used to map layers below 100 m, as well as the ice-bedrock interface. This radar is beyond the scope of this paper. Field data collection using these systems will be performed simultaneously, providing a fine-resolution characterization of the ice sheet from surface to bedrock. The altimeter provides annual and short-term information on the accumulation, while the accumulation radar provides information on the decadal scale variability. The depth sounder provides information on the century scale variability. Initial data collection occurred during the early spring 2009 Greenland field season; additional data collection will continue during future campaigns both in Greenland and Antarctica. System refinements will allow for this suite to be deployed on uncrewed aerial vehicles (UAVs), also being developed at the Center for Remote Sensing (CReSIS) at the University of Kansas.