Subglacial Topography of an Icefall Inferred From Repeated Terrestrial Laser Scanning

Information about ice thickness and subglacial topography is a key element for ice dynamics modeling and, consequently, for better understanding of current response of glaciers to climatic forcing. While there has been a substantial progress in the measurements of glacial surface, ice thickness measurements still suffer from limited coverage and strong interpolation. Furthermore, there are some glaciated areas where typical remote sensing techniques provide only limited data due to unfavorable climatic conditions and steep topography. A perfect example of such a feature is icefalls dominating landscapes of the maritime Antarctic. In order to close that gap, this letter presents a simple method of inferring the subglacial topography based on repeated terrestrial laser scanning of the ice surface and inverse shallow ice approximation modeling. Emerald Icefalls, King George Island, were surveyed twice within eight-day period, allowing to derive ice surface velocity field by feature tracking analysis and to estimate ice thickness and the subglacial topography. Calculated ice thickness is low, with the mean value of 72 +/- 18 m. Therefore, in line with former studies, the overall ice flux of Emerald Icefalls is small despite their relatively high surface ice flow velocities.