Modelling calving over the last 1000 years of a Greenlandic tidewater glacier during advance and retreat

50% of mass loss from the Greenland Ice Sheet in recent decades is due to calving from tidewater glaciers (TWG). However, the relationship between climate and calving remains uncertain. While calving parameters in glacier models can replicate observed glacier retreat, they need validation against longer-term records of ice margin advance and retreat. By contextualizing both the advance and retreat of a Greenlandic TWG, Kangiata Nunaata Sermia, KNS, over centennial to millennial timescales, we can minimize the impact of short-term climate variations and assess if modelled climate-glacier interactions are biased toward retreat due to processes operating over decadal timescales. 

Our model is validated against a well-constrained millennial-scale record of advance and retreat from a fast-flowing TWG in southwest Greenland. Our key research questions are: How do calving laws perform when modelling the advance of a grounded Greenlandic TWG? And how do calving law tuning parameters relate to physical processes, such as climate and fjord geometry? By comparing four calving laws and exploring a physical basis for glacier-specific tunning, we aim to better constrain calving fronts in glacier models and improve the capacity for predictive calving modelling.

A previous Greenland wide study suggested that the von Mises law better replicates decadal retreat, but our results show it lacks sensitivity to advance and, to avoid numerical instability, requires transient tuning for retreat. We further investigate the sensitivity of other calving laws, including eigen calving, height-above-buoyancy, and crevasse-water-depth.