Search

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]

Abstract. Grounding line discharge is a key component of the mass balance of the Antarctic Ice Sheet. Here we present an estimate of Antarctic Ice Sheet grounding line discharge from 1996 through to last month. We calculate ice flux at up to 100 m resolution through 16 algorithmically-generated flux gates, which are continuous around Antarctica. We draw on a range of ice velocity and thickness data to estimate grounding line discharge. For ice thickness, we use four bed topography datasets, two firn models and a temporally varying ice surface. For the ice velocity, we utilise a range of publicly-available ice velocity maps at resolutions ranging from 240 x 240 m to 1000 x 1000 m, as well as new, 100 x 100 m monthly velocity mosaics derived from intensity-tracking of Sentinel-1 image pairs, available since October 2014. The pixel-based ice fluxes and ice flux errors are integrated within all available Antarctic ice stream, ice shelf and glacier basins. Our dataset also includes the contributions to discharge from changes in ice thickness due to surface lowering, time-varying firn air content and surface mass change between the flux gates and grounding line. We find that Antarctic Ice Sheet grounding line discharge increased from 1,990 ± 23 Gt yr-1 to 2,205 ± 18 Gt yr-1 between 1996 and 2023, much of which was due to acceleration of ice streams in West Antarctica but with substantial contributions from ice streams in East Antarctica and glaciers on the Antarctic Peninsula. The uncertainties in our discharge dataset primarily result from uncertain bed elevation and flux gate location, which account for much of difference between our results and previous studies. It is our intention to update this discharge dataset each month, subject to continued Sentinel-1 acquisitions and funding availability. [ABSTRACT FROM AUTHOR]