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Abstract. Antarctic ice shelves buttress the flow of the ice sheet but are vulnerable to increased basal melting from contact with a warming ocean and increased mass loss from calving due to changing flow patterns. Channels and similar features at the bases of ice shelves have been linked to enhanced basal melting and observed to intersect the grounding zone, where the greatest melt rates are often observed. The ice shelf of Thwaites Glacier is especially vulnerable to basal melt and grounding zone retreat because the glacier has a retrograde bed leading to a deep trough below the grounded ice sheet. We use digital surface models from 2010–2022 to investigate the evolution of its ice-shelf channels, grounding zone position, and the interactions between them. We find that the highest sustained rates of grounding zone retreat (up to 0.7 km yr−1) are associated with high basal melt rates (up to ∼250 m yr−1) and are found where ice-shelf channels intersect the grounding zone, especially atop steep local retrograde slopes where subglacial channel discharge is expected. We find no areas with sustained grounding zone advance, although some secular retreat was distal from ice-shelf channels. Pinpointing other locations with similar risk factors could focus assessments of vulnerability to grounding zone retreat.
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Basal mass balance and prevalence of ice tongues in the Western ross sea
Ice tongues at the fringes of the Antarctic ice sheet lose mass primarily through both basal melting and calving. They are sensitive to ocean conditions which can weaken the ice both mechanically or through thinning. Ice tongues, which are laterally unconfined, are likely to be particularly sensitive to ocean-induced stresses. Here we examine ice tongues in the Western Ross Sea, by looking into the factors affecting their stability. We calculate the basal mass change of twelve Antarctic ice tongues using a flux gate approach, deriving thickness from ICESat-2 height measurements and ice surface velocities from Sentinel-1 feature-tracking over the same period (October 2018 to December 2021). The basal mass balance ranges between −0.14 ± 0.07 m yr −1 and −1.50 ± 1.2 m yr −1 . The average basal mass change for all the ice tongues is −0.82 ± 0.68 m of ice yr −1 . Low values of basal melt suggest a stable mass balance condition in this region, with low thermal ocean forcing, as other studies have shown. We found a heterogeneous basal melt pattern with no latitudinal gradient and no clear driver in basal melt indicating that local variables are important in the persistence of ice tongues in the absence of a strong oceanographic melting force. Moreover, thanks to the temporal resolution of the data we were able to resolve the seasonal variability of Drygalski and Aviator Ice Tongues, the two largest ice tongues studied.
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- Award ID(s):
- 1929991
- PAR ID:
- 10411908
- Date Published:
- Journal Name:
- Frontiers in Earth Science
- Volume:
- 11
- ISSN:
- 2296-6463
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/feart.2023.1057761
