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.