Calving from horizontal forces in a revised crevasse-depth framework

Abstract. Calving is a key process for the future of our ice sheets and oceans, but representing it in models remains challenging. Among numerous possible calving parameterisations, the crevasse-depth law remains attractive for its clear physical interpretation and its performance in models. In its classic form, however, it requires ad-hoc and arguably unphysical modifications to produce crevasses that are deep enough to result in calving. Here, we adopt a recent analytical approach accounting for the feedback between crevassing and the stress field and varying the density of water in basal crevasses, and show that it removes the need for such ad-hoc modifications. After accounting for ice tensile strength and basal friction, we show that the revised formulation predicts that full-thickness calving should occur at flotation when the calving front ice thickness is greater than around 400 m. It also predicts no calving for ice thinner than around 400 m, suggesting that calving at such glacier fronts is not driven purely by horizontal forces. We find good observational support for this analysis. We advance the revised crevasse-depth formulation as a step towards understanding differing calving styles and a better representation of calving in numerical models.