A new ice shelf melt model that accounts for freshwater discharge and application to Denman Glacier, East Antarctica

Ice shelf basal melting is the primary mechanism by which the Antarctic Ice Sheet loses mass. While it is largely agreed upon that ocean forcing is the primary control on the rate at which basal melting ensues, recent modeling evidence suggests that localized melt maxima are located along deep grounding lines where large quantities of subglacial water are being discharged into sub-ice shelf cavities. As any change in the configuration of the grounding line can drastically influence the stress regime of the entire upstream grounded glacier, it is crucial we resolve this subglacial discharge-driven melting in a basal melt rate parameterization that can be used in standalone ice sheet models. Here, we build off of previous plume and box modeling work to derive a melt-rate scaling that is appropriate for freshwater discharge-driven ice shelf basal melting near Antarctic grounding lines. We also implement a simplified river-routine to route the plume that induces the sub-shelf melting and apply this melt parameterization in a forward simulation of Denman Glacier, East Antarctica. Using subglacial hydrology model outputs to constrain the discharge inputs, we find that this parameterization resolves both local maxima and the large-scale spatial distribution of melt beneath the ice shelves buttressing Denman, Totten, Cook, Thwaites, and Pine Island Glaciers. In the forward simulations of Denman Glacier, the melt contribution from subglacial discharge is required to reproduce present-day patterns of grounding line retreat. Under realistic 21st century ocean and subglacial forcing scenarios, Denman Glacier retreats upstream to a ~10 km prograde section of bed topography upon which the grounding line stabilizes. However, under enhanced forcing, it is possible that Denman Glacier's grounding line can overcome this pinning point and retreat inland into the deepest submarine trench on Earth by 2100.