Estimating Subglacial Water Geometry Using Radar Bed Echo Specularity: Application to Thwaites Glacier, West Antarctica

Airborne radar sounding is an established tool for observing the bed conditions and subglacial hydrology of ice sheets and glaciers. The specularity content of radar bed echoes has also been used to detect the hydrologic transition of a subglacial water system from a network of distributed canals to a network of concentrated channels beneath the Thwaites Glacier. However, the physical dimensions of the distributed water bodies in these networks have not been constrained by observations. In this letter, we use a variety of simple radar scattering, attenuation, and cross-sectional models to provide a first estimate of the subglacial water body geometries capable of producing the observed anisotropic specularity of the Thwaites Glacier catchment. This approach leads to estimates of ice/water interface root mean square roughnesses less than about 15 cm, thicknesses of more than about 5 cm, lengths of more than about 15 m, and widths between about 0.5 and 5 m.