Antarctic ice shelves threatened by ocean warming
A new study shows that 60% of the ice shelves surrounding Antarctica could disappear by 2300 if greenhouse gas emissions are not curbed. The progressive loss of these “mechanical brakes” would allow the Antarctic ice sheet to flow much more rapidly into the ocean, potentially raising global sea level by up to ten metres in the long term.
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ntarctica is fringed by a belt of gigantic floating ice shelves, several hundred metres thick and grounded on coastal margins and the seafloor. These ice shelves play a crucial role by acting as buttresses that hold back the ice resting on the continent. Without them, the Antarctic ice sheet would discharge much more rapidly into the ocean, strongly increasing sea level.
"Many studies have already examined the future stability of Antarctic ice shelves, but they often focused on surface melt or atmospheric warming," explains Clara Burgard, CNRS researcher at the Institut Pierre Simon Laplace. "With our team, we adopted a more comprehensive approach by taking into account both atmospheric warming and, crucially, the warming of the ocean that bathes the underside of the ice shelves."
The researchers performed numerical simulations of the evolution of sixty-four ice shelves around Antarctica under different greenhouse gas emission scenarios, in order to determine under which conditions these ice shelves become "non-viable", that is, too thinned or too weakened to continue to effectively buttress the grounded ice sheet.
In a high-emissions scenario, with warming approaching 12 °C by 2300, thirty-eight of the sixty-four ice shelves studied lose their structural integrity. This loss of a "mechanical brake" could, in the long term, contribute to a sea-level rise of up to ten metres. In a more ambitious climate scenario, which would limit warming to below 2 °C by 2300, only a single ice shelf would become non-viable, and the risk would not increase substantially until after 2250. In other words, the future of the ice shelves depends very directly on our emissions pathway.
"The study shows that the destabilisation of ice shelves will not occur overnight," explains Christoph Kittel, climatologist at ULiège and co-author of the study, "but that it could accelerate markedly from the end of the 21st century onwards. Most of the simulated declines start around 2085 and peak around 2170. Even if these time horizons may seem distant, the decisions that determine them are being taken today. Ice shelves have enormous inertia. Once they have thinned and fractured, it is practically impossible to reverse the process."
The ocean as the main driver of destabilisation
A key result of this work is the identification of the ocean as the principal driver of the loss of ice-shelf viability. Warming and changes in the circulation of deep waters bring more warm water into contact with the base of the ice shelves, accelerating basal thinning. "Among other tools, we use the MAR (Regional Atmospheric Model), developed at ULiège, to quantify the impact of the atmosphere on ice-shelf weakening," continues Kittel. "It allows us to finely simulate the exchanges of energy, snow, and ice between the atmosphere and the ice-sheet surface, and to combine this information with ocean-warming data. This coupled approach is essential for estimating when the structure of the ice shelves will tip into a non-viable state."
The authors emphasise that their estimates are likely conservative. The simulations account for thermally driven thinning, but other processes that could trigger ice-shelf collapse such as fracturing, crevasse propagation, rift formation, or major calving events, are only weakly, if at all, represented. In reality, some ice shelves may therefore collapse earlier than the models suggest.
Scientific reference
Burgard C., Jourdain N.C., Mosbeux C., Caillet J., Mathiot P. and Kittel C., Ocean warming threatens the viability of 60% of Antarctic ice shelves. Nature 647, 102–108 (2025). doi.org/10.1038/s41586-025-09657-w
