When the Hektoria Glacier in Antarctica suddenly began a rapid retreat three years ago, scientists were baffled. The glacier pulled back more than eight kilometres in just two months at the end of 2022. A new study now claims to have solved the mystery. Researchers suggest that Hektoria may be the first modern case where the front of a glacier resting on the seabed became suddenly unstable. This process could cause sea levels to rise faster if it occurred elsewhere in Antarctica. Yet some scientists argue that the glacier’s edge was already floating, making the event less unusual than it seems. Floating glacier tongues, or ice shelves, are far more vulnerable to collapse because warm water can easily melt them from below.
Unraveling the mystery
No one disputes that Hektoria has changed dramatically. Satellite data shows the glacier’s front retreated about 25 kilometres between January 2022 and March 2023. Lead author Naomi Ochwat, a research affiliate at the University of Colorado Boulder and postdoctoral researcher at the University of Innsbruck, described the investigation as a scientific “whodunnit.” The story begins in 2002, when the Larsen B ice shelf in the eastern Antarctic Peninsula collapsed. Roughly 3,250 square kilometres of ice—an area the size of Cambridgeshire—disappeared. Larsen B had held Hektoria in place. Once it was gone, the glacier sped up and thinned dramatically. The bay once filled by the ice shelf later became packed with sea ice anchored to the seabed, helping to stabilise the glacier temporarily. But in early 2022, that sea ice broke apart.
After that, Hektoria lost more floating ice as massive flat-topped icebergs broke off. The glacier behind them accelerated and thinned. Iceberg calving is normal for glaciers, though climate change makes such losses more frequent. But something different happened later that year. Researchers say the glacier’s front was no longer floating but grounded on the seabed. In just two months, Hektoria retreated 8.2 kilometres—almost ten times faster than any grounded glacier ever recorded. The study, published in Nature Geoscience, calls this change extraordinary.
The role of the ice plain
Scientists think this dramatic shift may stem from an “ice plain”—a flat section of bedrock beneath the glacier. As the ice thinned, buoyant forces from the ocean might have lifted it almost instantaneously. That lift could have caused large chunks to break off and the glacier to retreat rapidly. “Glaciers don’t usually retreat this fast,” said co-author Adrian Luckman, a geography professor at Swansea University. “These conditions might be unique, but they show what could happen elsewhere in Antarctica where glaciers rest lightly on the seabed and sea ice loses its grip,” he added.
The researchers note that this process has never been observed in modern times, though markings on the seafloor suggest it occurred in Earth’s past. “Hektoria is small,” said Dr Ochwat, “but if this happens in other parts of Antarctica, the impact on sea-level rise could be huge.” She warned that similar areas, such as the Thwaites Glacier—known as the “doomsday glacier”—could trigger a rise of 65 centimetres if they melt entirely. “We must find out whether other ice plains face the same risk,” she added.
A divided scientific community
Not everyone agrees with the study’s conclusions. The dispute centres on the “grounding line,” the point where a glacier stops touching the seabed and starts to float. “This study gives us a glimpse of what could be the fastest retreat ever seen in modern Antarctica,” said Dr Frazer Christie, a glaciologist and senior Earth observation specialist at Airbus Defence and Space. “But there’s serious disagreement about the exact position of Hektoria’s grounding line, because radar satellites struggle to measure it in such fast-moving regions.”
That uncertainty matters. If the glacier section was actually floating, the retreat would represent ordinary iceberg calving, not an unprecedented event. “The mechanism is plausible,” said Dr Christine Batchelor from Newcastle University, “but without knowing where the grounding zone really was, we can’t be sure this was the case at Hektoria.”
A changing Antarctic landscape
Despite differing interpretations, scientists agree on one thing: Antarctica is changing at alarming speed. “We may debate what caused Hektoria’s retreat,” said Professor Anna Hogg from the University of Leeds, “but we all agree that polar changes are shockingly fast—faster than we imagined a decade ago.” She urged for more satellite data to monitor these rapid transformations. Understanding what drives them, she said, is essential for predicting how quickly global sea levels will rise.
