Drivers of Basal Melt Variability for Pine Island Glacier Ice Shelf: Ocean Forcing Versus Geometric Feedback

Since the 1970s, Pine Island Glacier has exhibited thinning, acceleration, and retreat. During the last decade, the ice shelf has undergone major geometric changes, whilst the quantity and temperature of modified Circumpolar Deep Water on the Amundsen Sea continental shelf fluctuated significantly. Untangling how these factors modulate ice-shelf basal melt rates is critical, as ocean-driven melt may be mitigated through emission reductions, whereas geometry-driven retreat may be irreversible. We use ocean model experiments to partition the relative importance of ice geometry and ocean temperature changes in driving melt variability between 2011 and 2021. Simulations use observed ice-shelf geometries from CryoSat-2 and ocean boundary conditions from moorings in Pine Island Bay. Temporal variability of melt and implied ice loss during this period was largely controlled by ocean conditions, while geometric evolution primarily controlled the spatial distribution of melt through cavity circulation reconfiguration, with a non-negligible impact on buttressing.