A basal melt parameterization for the simulation of freshwater discharge-driven melt for warm Antarctic ice shelves

Abstract Melting of floating ice shelves is one of the key processes determining the mass balance of the Antarctic ice sheet. Freshwater discharge at the grounding line provides an additional buoyancy source, causing local melt enhancement near the grounding line and possibly faster grounding line retreat. The impact of freshwater discharge has been studied extensively for the Greenland ice sheet, but it is only beginning to be assessed for Antarctic ice shelves. In this study, a basal melt parameterization that incorporates both the effects of freshwater discharge and the ocean heat is derived. Based on a simplified melt expression, convergence solutions of a meltwater plume model are used to approximate the plume thermal forcing and velocity for the region near the grounding line. Deviations of the plume solutions from the convergence solutions occur due to nonlinearities associated with the effect of freshwater influx in combination with that of basal geometries and ambient conditions. Those nonlinearites are described based on power law dependencies in the limit of small heat advection within the plume. This yields a new melt formulation that can be applicable to warm ice shelf cavities. Close agreements are observed when comparing the parameterization with solutions of the plume model for a wide range of freshwater influxes and oceanic conditions. The two-dimensional extension of the parameterization captures the local melt enhancement up to ~ 140 m yr −1 observed near the grounding line of Pine Island Glacier.