Future (2015-2100) Antarctic-wide ice-shelf firn air depletion from a statistical firn emulator

Antarctic firn is critical for ice-shelf stability because it stores meltwater that would otherwise pond on the surface. Ponded meltwater increases the risk of hydrofracture, and subsequent potential ice-shelf collapse. Here, we use output from a firn model to build a computationally simpler emulator that uses a random forest to predict ice-shelf firn air content (FAC) based on climate conditions. We find that summer air temperature and precipitation are the most important climatic features for predicting FAC. By 2100, Larsen C Ice Shelf is most at risk of firn air depletion, while the larger Ross and Ronne-Filchner are likely to experience little FAC change. Variability in Earth System Model projections is the largest uncertainty source regarding future FAC predictions. In fact, the model uncertainty, described by the firn air depletion spread from CMIP6 models in the SSP3-7.0 and SSP5-8.5 emission scenarios, is larger than the firn air depletion range across the emission scenarios.