Exploring causes of an intermittent topographic anomaly at the calving front of Helheim Glacier, South East Greenland

Iceberg calving has been identified as a key process for understanding the future stability of the Greenland Ice Sheet. Increases in calving rate can reduce the size and extent of ice shelves and tongues causing a decrease in backstress and a subsequent increase in ice discharge from the ice sheet's interior. For this reason calving has been identified as a major contributor to rapid ice sheet changes. In order to improve understanding of these processes, improved models must be developed to reproduce observed glacier behaviour using real glacier geometry in 3D calving models. However, this will require with improved observations of glacier frontal position and flow velocity. Here we present results from a time-series of hourly photographs of the near-terminus surface, calving front and proglacial ice mélange of Helheim Glacier in southeast Greenland, collected using stereo, terrestrial camera installations in the summers of 2010, 2011 and 2012. Using these images with camera calibration and ground-truth data, we have generated daily 5 m resolution digital elevation models (DEMs) from which detailed measurement of frontal position, volume loss, glacier velocity and ice mélange displacement are be made. Additionally, using supporting ASTER-derived DEMs, we have identified a topographic anomaly near the calving margin that currently cannot be explained but could be indicative of processes occurring subglacially and may provide important insight into calving dynamics. The anomaly is presented as a topographic low running parallel to and within 1.5 km of the calving front but that is not consistent in position or present in all years of observation even where frontal geometry is similar. These data represent a low-cost approach to monitoring and quantifying calving processes that will contribute to improving predictions of future sea level contributions from the GrIS.