Simulating 3D calving dynamics at Thwaites Glacier

Recent advances in the Elmer/Ice modelling suite have allowed 3D simulation of unrestricted calving geometries at tidewater glaciers such as Jakobshavn Isbrae. We present the first use of this model in an Antarctic setting. The more stochastic nature of calving at Antarctic ice sheets when compared to a Greenlandic setting has discouraged the development of calving laws and models. For shorter term calving simulations, it is sufficient to determine the local attractor or pinning point where the terminus stabilises following a transient period of retreat or advance. Importantly, this can only be achieved through a position-based law, as a positional attractor is independent of velocity.

Using a deterministic position-based crevasse depth calving law it is possible to simulate the observed calving behaviour at the western ice front of Thwaites Glacier. The calving law identifies the attractor point beyond which ice will calve following a variable but short delay. The geometric attractor is defined by local topography along with grounding zone dynamics. Beyond this point there are a lack of lateral or basal pinning points, so any downstream ice is effectively lost from the system. More generally, across the floating extensions of Thwaites Glacier, the model reliably predicts regions of crevasse formation. Accurately simulating crevasse formation on ice shelves along with determining the attractor within the glacier retreat and advance cycle is the first step towards a reliable Antarctic calving law.