Predicting buoyancy stresses and ice shelf calving with viscous and elastic frameworks

The Antarctic Ice Sheet loses mass via its ice shelves predominantly through two processes: basal melting and iceberg calving. Iceberg calving is episodic and infrequent, and not well parameterized in ice sheet models. The relative role of elastic, viscous and plastic rheologies in such mechanism is usually hard to untangle. Here, we investigate the impact of such rheologies on the distribution of stresses at the ice shelf front in the context of the “footloose” mechanism. This mechanism is triggered by submerged ice protrusions at the ice shelf front, usually revealed by a positive flexure of the ice shelf surface close to the front (called a rampart-moat), with large protrusions eventually leading to fracturing of the ice shelf. More specifically, we contrast elastic and viscous results to identify the different roles they play in the deformations of the ice shelf, the rate and magnitude of calving events. By comparing our results with rampart-moat observations, we show that, although the bending stresses in both frameworks share some characteristics, their differences have important implications for modeling the calving process. In particular, the elastic model predicts that maximum stresses arise farther from the ice front than does the viscous model, therefore suggesting larger calving events. We further find that an elastic rheology would likely lead to more frequent calvings, compared to a viscous one.