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Basal melting is a major component of Antarctic ice mass loss. It is mainly driven by the circulation of water in ice shelf cavities. One approximation of this circulation is by models of buoyant plumes rising along the ice shelf base. For large-scale ice sheet models, a local melt parameterization of plume models that can be applied at an ice shelf-wide scale is desirable, and such a parameterization has recently been proposed and shown to perform well compared to a spatially resolved plume model when the ice shelf profile is fixed. In this study, we test the local parameterization for a dynamically evolving ice shelf, which allows for feedbacks between basal slope and melt rate. We find that these feedbacks enhance melt for steep basal slopes and reduce melt for small slopes. This decreases the parameterization performance, and under certain conditions the parameterization introduces an unphysical melt discontinuity. This can lead to large differences in the predicted melt rate and ice shelf length compared to the nonlocal plume model. More generally, our findings suggest that i) local parameterizations should be applied with caution in coupled ice–ocean frameworks, and ii) melt parameterizations should be evaluated in coupled settings to avoid unwanted behavior. 

Wave erosion of ice cliffs is one of the main mechanisms for waterline ablation of icebergs, glacier fronts and ice-shelf fronts. Despite its importance, this process is neither well understood nor extensively tested in controlled experiments and only coarsely parameterised in geophysical and climate models. We examine the surface-wave-driven melting of a vertical ice wall using both theory and laboratory experiments, with an emphasis on the flow-induced heat transport in the theory and on measurements of the melt rate profile under different wave conditions in the experiments. In both the theory and the experiments, we find that the wave-induced melt rate decays exponentially with depth. By analysing the oscillatory boundary layer flow, we find that an approximate wave-averaged balance of heat transport is given by horizontal diffusion and vertical advection due to an Eulerian boundary layer streaming current. By solving for this balance and obtaining the wave-averaged temperature field, we find an explicit expression for the wave-induced melt rate. Experimental data show a good match to this expression, especially for larger wave amplitudes and colder water temperatures. 

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 at floating ice shelves, and we generalise the framework by adding non-zero ice tensile strength and basal friction and by applying it to grounded marine-terminating glaciers. We show that the revised formulation removes the need for ad hoc modifications and predicts that full-thickness calving should occur when grounded glaciers reach flotation, provided the calving front ice thickness is greater than around 400 m. The revised formulation 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 from both grounded marine-terminating glaciers and floating ice shelves 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. 

Abstract. Ice shelf calving constitutes roughly half of the total mass loss from the Antarctic ice sheet. Although much attention is paid to calving of giant tabular icebergs, these events are relatively rare. Here, we investigate the role of frontal melting and stresses at the ice shelf front in driving bending and calving on the scale of ∼100 m, perpendicular to the ice edge. We focus in particular on how buoyant underwater “feet” that protrude beyond the above-water ice cliff may cause tensile stresses at the base of the ice. Indirect and anecdotal observations of such feet at the Ross Ice Shelf front suggest that the resulting bending may be widespread and can trigger calving. We consider satellite observations together with an elastic beam model and a parameterization of wave erosion to better understand the dynamics at the ice shelf front. Our results suggest that on average frontal ablation rather consistently accounts for 20±5 m yr−1 of ice loss at Ross Ice Shelf, likely mostly due to wave erosion and smaller-scale, 𝒪(100 m), foot-induced calving. This constitutes only ∼2 % of the total frontal mass loss (since near-front ice velocities are ∼1000 m yr−1). Observational evidence suggests that sporadic larger events can skew this rate (we document one foot-induced calving event of size ∼1 km). Stresses from foot-induced bending are likely not sufficient to initiate crevassing but rather act to propagate existing crevasses. In addition, our results support recent findings by Buck (2024) that additional bending moments, likely due to temperature gradients in the ice, may play a role in driving frontal deflections. The highly variable environment, irregularity of pre-existing crevasse spacing, and complex rheology of the ice continue to pose challenges in better constraining the drivers behind the observed deformations and resulting calving rates.