Abstract
AbstractThe Wilkes Subglacial Basin in East Antarctica contains ice equivalent to 3–4 m of global mean sea level rise and is primarily drained by Cook Glacier. Of concern is that recent observations (since the 1970s) show an acceleration in ice speed over the grounding line of both the Eastern and Western portions of Cook Glacier. Here, we use a numerical ice-flow model (Úa) to simulate the instantaneous effects of observed changes at the terminus of Cook Glacier in order to understand the link between these changes and recently observed ice acceleration. Simulations suggest that the acceleration of Cook West was caused by a retreat in calving-front position in the 1970s, potentially enhanced by grounding-line retreat, while acceleration of Cook East was likely caused by ice-shelf thinning and grounding-line retreat in the mid-1990s. Moreover, we show that the instantaneous ice discharge at Cook East would increase by up to 85% if the whole ice shelf is removed and it ungrounds from a pinning point; and that the discharge at Cook West could increase by ~300% if its grounding line retreated by 10 km.
Highlights
The East Antarctic Ice Sheet (EAIS) is the single largest potential contributor to future global mean sea level rise, containing the equivalent of 54 m (Morlighem and others, 2020)
Model simulations of calving-front retreat for Cook West are able to produce changes of a similar magnitude to observations of ice-speed acceleration following the 1973 calving event, with this acceleration enhanced by a potential grounding-line retreat
When thinning is combined with a simulated grounding-line retreat an acceleration in ice speed of a comparable magnitude can be obtained, indicating that the grounding line at Cook East was previously in a more advanced location
Summary
The East Antarctic Ice Sheet (EAIS) is the single largest potential contributor to future global mean sea level rise, containing the equivalent of 54 m (Morlighem and others, 2020). Individual studies of its mass balance range from + 61 ± 73 Gt a−1 (from 2008 to 2015: (Gardner and others, 2018) to − 51 ± 13 Gt a−1 (from 1979 to 2017: Rignot and others, 2019), with the latest reconciled estimate given as 5 ± 46 Gt a−1 (from 1992 to 2017: Shepherd and others, 2018). Notwithstanding these uncertainties in the overall mass balance of the EAIS, some regions appear to be losing mass, Wilkes Land, which sits over the Aurora Subglacial Basin (Li and others, 2016; Rignot and others, 2019; Velicogna and others, 2020). Mengel and Levermann (2014) suggested that the grounded ice is currently held back by an ‘ice plug’ that, were it to be removed by future ice retreat or thinning, would accelerate the flow of grounded ice and increase Cook Glacier’s contribution to future sea level rise
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