Toward new maps of basal melt rate in grounding zones with tidal flexure from ICESat-2

Basal melt rate in the grounding zone is one of the single most important and least-well constrained parameters in modeling the rate and amount of future sea level rise. Sub-ice shelf basal melt rate can be calculated by continuity of mass provided that local ice thickness is well known. However, continent-wide maps of ice thickness that rely on the hydrostatic assumption may underestimate ice thickness near the grounding line. Here, we jointly invert for ice shelf thickness and effective Young’s modulus in the grounding zones of three basins on the Ronne-Filchner Ice Shelf (FRIS or RFIS) based on an elastic beam model of the tidal flexure of ice shelves to make new estimates of basal melt rate in the grounding zone. We show that uncertainty in ice thickness gradient drives uncertainty in the spatial pattern of basal melt rate: adding, eliminating, or moving oceanographic features such as freeze-on bands. This has implications for the set of admissible parameterizations of basal melt rate in models that project the evolution of the Antarctic Ice Sheet in the coming decades and centuries.