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 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 article, we report a simulation study to assess the feasibility of realizing three science goals: the retrieval of: 1) $T_{i}$ at 10 m depth to within 1 K; 2) vertically averaged $T_{i}$ to within 1 K; and 3) 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.