Modelling environmental influences on calving at Helheim Glacier in eastern Greenland

Calving is an important mass-loss process for many glaciers worldwide, and has been assumed to re- spond to a variety of environmental influences. We present a grounded, flowline tidewater glacier model using a physically-based calving mechanism, applied to Helheim Glacier, eastern Greenland. By qualitatively examining both modelled size and frequency of calving events, and the sub- sequent dynamic response, the model is found to realistically reproduce key aspects of observed calving behaviour. Experi- ments explore four environmental variables which have been suggested to affect calving rates: water depth in crevasses, basal water pressure, undercutting of the calving face by sub- marine melt and backstress from ice melange. Of the four variables, only crevasse water depth and basal water pres- sure were found to have a significant effect on terminus be- haviour when applied at a realistic magnitude. These results are in contrast to previous modelling studies, which have sug- gested that ocean temperatures could strongly influence the calving front. The results raise the possibility that Greenland outlet glaciers could respond to the recent trend of increased surface melt observed in Greenland more strongly than pre- viously thought, as surface ablation can strongly affect water depth in crevasses and water pressure at the glacier bed.