Inferring subglacial topography of the Emerald Icefalls (King George Island, Antarctica) from ice surface terrestrial laser scanning

Abstract

Information about ice thickness and sub glacial topography is critical for ice dynamics modelling and, consequently, for better understanding of current response of glaciers to climatic forcing. While there is a great progress in measurements of glacial surface, ice thickness measurements have limited coverage and are usually heavily interpolated. Still, there are some areas where typical remote sensing techniques fail because of adverse climatic conditions, mainly persistent cloud cover, and very steep topography. A perfect example of such feature are icefalls dominating landscapes of the maritime Antarctic. In order to close that gap, a simple method based on repeated terrestrial laser scanning of the ice surface is proposed. Based on such measurements, inverse Shallow Ice Approximation ice flow modelling was applied to infer the sub glacial topography of the Emerald Icefalls, King George Island. The icefalls were surveyed twice within 8 day period, allowing to perform feature tracking analysis and, hence, to derive surface ice flow velocity field. The measured flow velocities are spatially highly variable, suggesting the existence of four separated trunks. The estimated ice depths are low with the mean value of 30.3±8.3 m. Therefore, as suggested by previous studies, the overall ice flux of Emerald Icefalls is low despite relatively high surface ice flow velocities.