Feasibility of Estimating Ice Sheet Internal Temperatures Using Ultra-Wideband Radiometry

Although ice sheet internal temperature is a first-order control on glacier dynamics, relatively few in situ borehole temperature profiles exist. The ultra-wideband software-defined microwave radiometer (UWBRAD) was designed to estimate internal ice sheet temperature ( T i ) by measuring microwave brightness temperatures ( T b ) from 0.5 GHz to 2 GHz. The retrieval of T i from T b is not straightforward, however, due in part to the complicating effects of ice density fluctuations on T b . In this paper, we report a simulation study to assess the feasibility of realizing three science goals: the retrieval of a) T i at 10 m depth to within 1 K; b) vertically-averaged T i to within 1 K; and c) the vertical T i profile to within 1 K RMSE. Two analyses along the Greenland ice divide are presented. First, we assess the ideal UWBRAD T i retrieval precision via the Cramér-Rao Lower Bound (CRLB). Second, we perform a "Virtual Experiment" (VE) using synthetic UWBRAD observations. Both the CRLB and VE analyses indicate that the science goals are achievable with the caveats that ice thickness and UWBRAD T b precision impact performance. Assuming a UWBRAD T b precision of 0.5 K, and for places where ice sheet thickness is less than 3 km, all science goals can be achieved. The results of the study provide a strong indication of the potential of UWBRAD to provide valuable Greenland ice temperature profile information to the scientific community.