Full-Stokes Modelling of a Calving Glacier Using a Damage-Mechanics Approach to Represent Crevassing

Iceberg calving rate is thought to be a key control on the dynamics of tidewater glaciers. Retreat of these glaciers is associated with increased flow velocities and thinning, and therefore plays an important role in determining the mass-balance of the glacier (or ice sheet, in the case of outlet glaciers). The development of realistic, physically-based numerical models of the calving process is a necessary step towards predicting the response of tidewater glaciers to global climate change. However, it is difficult to represent the full complexity of processes active at a calving front in a numerical model. A particular challenge is in representing the bulk effect of crevasse processes at the calving front, while avoiding having to model each crevasse individually, which would be computationally impractical. The model we present here parameterizes the effect of crevasses on the rheology and stress balance of ice, and defines a prognostic relationship to determine the time-evolution of the crevasse field. Calving takes place when the crevassed region either penetrates the depth of the glacier or reaches the water line. We test the model in a 2D vertical slice configuration, and solve the Stokes stress balance using the multi-physics code Elmer. We present the results of tests using idealised geometry, and compare them with results for alternative published calving laws and glacier models.