Mechanical failure to drive the glacier collapse feature at Rhonegletscher, Switzerland

Rapid climate modifications perturb the long-term dynamic equilibrium of many natural systems. Polar and high-altitude regions such as alpine environments represent locations where perturbations such as glacier collapse features, become visible. Glacier collapse features are characterized by a circular depressions on the ice surface, are bounded by low-angle crevasses and are the surface expression of a cavity developing most often over a subglacial channel, commonly occurring at the glacier snout. Understanding the physical processes governing the collapse feature dynamics is essential to assess hazards and processes related to them, such as, rapid glacier length variations, snout collapses and sudden blockage of the subglacial drainage system.

Field observations from an on-going collapse feature developing at the snout of Rhonegletscher (Switzerland) in Summer 2022 suggest mechanical failure of ice lamellas from the underlying cavity roof to drive the collapse. In order to test this hypothesis, namely mechanical failure to drive glacier collapse features, we developed full-Stokes 2D and 3D mechanical models implementing a temperature and pressure dependent visco-elasto-plastic rheology. We use the extensive dataset from Rhonegletscher to constrain the numerical models to predict possible failure patterns as function of increasing cavity size. We use vertical displacement located in the centre of the collapse feature to validate our models. Preliminary results show the formation of tension failure patterns on the ice surface at locations coinciding with the low-angle circular crevasses. The model results will advance our understanding of the physics of collapse features and provide predictive tools to assess future occurrences and their related risks.