Terrestrial stereo photogrammetry reveals buoyancy-driven calving dominated summer dynamic mass loss at Helheim Glacier, southeast Greenland

Abstract:

Iceberg calving is responsible for a significant proportion of annual mass loss from marine-terminating glaciers and is believed to be a major factor in the rapid demise of paleo-ice sheets. Recent forecasts of sea-level contributions from the main outlet glaciers of the Greenland Ice Sheet find the majority of mass-loss will be dynamic in origin (i.e. driven by glacier flow and calving) over the next two centuries. However, despite the use of increasingly realistic, physically-based approaches, current models remain a coarse approximation of real calving mechanisms due largely to a lack of observations of glacier geometry required for 3D time-evolving models. We applied novel digital photogrammetric methods to stereo time-lapse imagery to generate a high temporal and spatial resolution record of daily digital elevation models of the calving margin of Greenland’s Helheim Glacier during the summers of 2010 and 2011. Our results show that during these summers large (>1 km3) calving events driven by buoyant flexure and basal crevasse propagation dominated dynamic mass loss at Helheim. This calving mechanism, common at Helheim and likely elsewhere in Greenland, is not well understood but is clearly an important first-order control on the ice sheet’s future contribution to sea-level.