Regime-shifts in ice-shelf melt could trigger irreversible ice loss from the Antarctic Ice Sheet

Changes in ocean conditions surrounding the Antarctic ice sheet, and the impact on melt rates beneath buttressing ice shelves, is one of the largest sources of uncertainty in future ice loss projections. If conditions were to suddenly undergo a regime-shift from cold to warm, melt rates could increase drastically and trigger large and potentially irreversible changes in the interior of the ice sheet. Here, we take an ensemble of ocean-circulation model melt rates as input to an ice-sheet model, to quantify ice loss and the potential for irreversible retreat under such warm conditions. We find that the currently cold-cavity basins of the Filchner-Ronne and Ross ice shelves, in contrast to present-day, could become large contributors to future sea level relevant ice loss. In major basins in West Antarctica, we find high-melt rates can trigger instances of irreversible grounding line retreat, which could only be recovered if arguably unattainable melt rate conditions prevailed over timescales of 100s of years.