Heterogeneous Basal Thermal Conditions Underpinning the Adélie‐George V Coast, East Antarctica.

Adélie‐George V Land in East Antarctica, encompassing the vast Wilkes Subglacial Basin, has a configuration that could be prone to ice sheet instability: the basin's retrograde bed slope could make its marine terminating glaciers vulnerable to warm seawater intrusion and irreversible retreat under predicted climate forcing. However, future projections are uncertain, due in part to limited subglacial observations near the grounding zone. Here, we develop a novel statistical approach to characterize subglacial conditions from radar sounding observations. Our method reveals intermixed frozen and thawed bed within 100 km of the grounding‐zone near the Wilkes Subglacial Basin outflow, and enables comparisons to ice sheet model‐inferred thermal states. The signs of intermixed or near thawed conditions raises the possibility that changes in basal thermal state could impact the stability of Adélie‐George V Land, adding to the region's potentially vulnerable topographic configuration and sensitivity to ocean forcing driven grounding line retreat. Plain Language Summary: East Antarctica's Adélie‐George V Land has been relatively stable over the last few decades. However, this region contains the Wilkes Subglacial Basin, which has a downward‐sloping bed inland of the grounding zone. This could make irreversible retreat possible if warming seawater off the coast enters beneath the ice sheet. However, predicting the region's vulnerability is difficult, in part, because there is limited information about the conditions beneath the ice sheet. In this study, we develop a new statistical approach to synthesize radar sounding data and classify the conditions at the ice‐bed interface into frozen‐bed and thawed‐bed, which can then provide comparisons to ice sheet model output. We find that areas near the outflow of the Wilkes Subglacial Basin, critical in maintaining the stability of the region, might consist of mixed frozen‐bed and thawed‐bed or near‐thawed conditions on the scale of tens of kilometers across. This finding is important since the extent of basal thaw affects how easily ice can flow or slide over the bed. If parts of the bed are close to thawed, this could make Adélie‐George V Land more sensitive to climate forcing, possibly resulting in mass loss. Key Points: We develop an adaptable statistical framework using radar sounding data to classify the basal thermal state of ice sheetsApplied to the Adélie‐George V Coast, the framework reveals a mix of frozen and thawed‐bed, along with confidence in the classificationsAreas maintaining the region's stability have varied thermal states and we consider how this could increase sensitivity to climate forcing [ABSTRACT FROM AUTHOR]