The melting of glaciers has a serious impact on sea level rise. But it is currently difficult to predict how stable or endangered the glaciers in the Arctic and Antarctic are. Researchers have now documented and examined an extreme case: The Hektoria Glacier in Antarctica retreated by more than eight kilometers within just two months in 2022 and lost half of its ice mass in the process. The study shows that geographical conditions in particular contributed to this massive ice loss. The results help to assess the risk for other glaciers more reliably.
As global warming increases, the glaciers at the poles are melting more and more. However, they are not only influenced by the temperature, but also by numerous other factors. For example, if there is a stable cover of sea ice at the point where the glacier flows into the ocean, for example in the form of an ice shelf, this protects the glacier from losses. A non-icy, turbulent sea, on the other hand, can promote calving – a process in which large masses of ice suddenly break off from a glacier front.
Causes of the decline
“Understanding and predicting the instability of ocean-terminating glaciers represents one of the greatest challenges for predicting future sea level rise,” explains a team led by Naomi Ochwat from the University of Colorado at Boulder. In order to gain a deeper insight into the underlying processes, the researchers have now examined one of the most serious ice retreats ever documented: The Hektoria Glacier on the eastern Antarctic Peninsula lost around half of its mass in November and December 2022. Such glaciers typically retreat by a few hundred meters per year. At the Hektoria Glacier there were at least eight kilometers within these two months alone, including 2.5 kilometers in just two days.
But how did this come about? In search of an answer, Ochwat and her team analyzed satellite images and combined them with geophysical data. It became clear that for decades the Larsen B Bay, into which the glacier flows, was covered by an ice shelf. But in early 2022, this sea-floating, land-anchored ice sheet broke up. “The retreat of the glacier began immediately after the loss of the decades-old ice shelf and was accompanied by an almost six-fold increase in flow velocity,” report the researchers. As a result, the ice thickness of the glacier decreased significantly.
Vicious circle of ice loss
Another factor accelerated the devastating loss of ice: the glacier front lost its grip on the ground. Originally the ice there reached down to the seabed, but as the ice became thinner it was increasingly undermined by water. The buoyancy and movement of the sea then further destabilized the ice and caused large chunks of ice to break off. From then on, this process reinforced itself: “The loss of ice leads to less resistance and therefore to an acceleration of glacier movement,” explains Martin Truffer from the University of Alaska, who was not involved in the study. “This then leads to a loss of ice thickness as the ice flows away, and reduced adhesion of the ice to the ground. This causes higher calving rates and further acceleration: a kind of vicious circle.”
The results suggest that other glaciers with similar conditions can also be easily destabilized. The Hektoria Glacier is comparatively small, so its massive calving has had little impact on sea levels. Nevertheless, Ochwat’s colleague Ted Scambos describes the ice loss on the Hektoria Glacier as a shock. “Such rapid retreat shows what could also happen with larger glaciers on the continent,” says Scambos. “If the same conditions occur in some other areas, this could significantly accelerate sea level rise.” Thanks to its findings, the current study can now help to improve climate models to take sudden changes in the calving behavior of glaciers into account.
Source: Naomi Ochwat (University of Colorado Boulder, USA) et al., Nature Geoscience, doi: 10.1038/s41561-025-01802-4