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

Abstract

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.

Evidence for and Against Temperate Ice in Antarctic Shear Margins From Radar‐Depth Sounding Data

“…The evidence we present here can help motivate and select future study sites for improved, temperature focused radar survey techniques like those proposed by Yardim et al (2022), Bienert et al (2023), andBroome et al (2023). Similarly, comprehensive ice flow models incorporating the 3D velocity field can be applied to specific field sites for data-model integration like Holschuh et al (2019) and assimilation of temperature into ice flow models can provide future improvements, similar to suggestions by Dawson et al (2024). We find evidence for temperate shear margins in 18 of 106 radar lines from Antarctic ice streams, but notably we observe evidence for non-temperate margins in 37 of 106 radar lines, which are concentrated in the Amundsen Sea Embayment (Figure 1a).…”

Sediment Freeze‐On and Transport Near the Onset of a Fast‐Flowing Glacier in East Antarctica

“…Alternatively, it is possible that basal units are produced upstream but thinned by ice flow or that the GHF is substantially higher here, such that the entire southern part of the survey area is melting at the base rather than freezing. However, sophisticated analyses of englacial attenuation, radar bed reflection and modeling would be necessary to better constrain the basal thermal state and thus allocate the presence of liquid water (Dawson et al, 2024;Schroeder et al, 2016).…”

Footprint of sustained poleward warm water flow within East Antarctic submarine canyons

“…The Ninnis Glacier is currently in contact with cold dense shelf water 34 , 35 , forming Adélie Land Bottom Water (25% of the global volume of Antarctic Bottom Water 36 , and references therein). However, changes in atmospheric and ocean circulation may have driven retreat in the past, as indicated by numerical ice sheet modeling ( 37 and references therein) and by ice and marine sediment cores (refs. 38 – 42 ).…”