In just 15 months, Antarctica’s Hektoria Glacier lost roughly 25 kilometers of grounded ice, about 15 miles, retreating faster than any glacier in the modern satellite record. The collapse, which unfolded between January 2022 and March 2023 along the eastern Antarctic Peninsula, accelerated violently at the end of 2022, when more than 8 kilometers of ice vanished in a single two-month window. The cause was not a spectacular surface fracture but something harder to see: warm ocean water reaching the glacier’s belly after a protective band of sea ice broke apart, thinning the ice from below until it lifted off the seabed and shattered into icebergs.
A peer-reviewed study published in Nature Geoscience in early 2025 documented the event in detail, calling it the fastest known retreat of grounded ice ever recorded by satellites. The findings have drawn renewed attention in 2026 as researchers monitor whether the conditions that triggered the collapse are returning to the region.
A glacier primed to fail
Hektoria Glacier sits in the Larsen B embayment, a stretch of coastline that lost its massive ice shelf in a dramatic breakup in 2002. That collapse removed the buttressing force that had braced glaciers like Hektoria and its neighbor, Green Glacier, for thousands of years. According to NASA’s Earth Observatory, both glaciers had been thinning steadily in the two decades since, their downstream ice plains growing shallower year by year.
By 2022, Hektoria’s ice plain was shallow enough that it did not take much additional thinning to push it toward flotation. But one thing had kept the glacier relatively stable through those years: a band of multi-year landfast sea ice that had formed along the embayment starting around 2011. That sea ice acted as a physical shield, blocking open-ocean swells and limiting warm water’s access to the glacier front.
In January 2022, the shield broke apart. Research published in The Cryosphere links the breakout to a combination of shifting wind patterns and warm, dry foehn winds that destabilized the ice cover. Once the barrier was gone, ocean swells could flex and fracture the exposed glacier margins, a process scientists had previously documented during the collapses of the Larsen A, Larsen B, and Wilkins ice shelves.
The fastest grounded retreat on record
The Nature Geoscience study, drawing on imagery from Landsat 8 and 9 satellites archived by the U.S. Geological Survey, tracked Hektoria’s terminus positions from October 2022 through March 2024. Analysts mapped both the grounding line and the coastline, confirming that the retreat involved ice firmly attached to the seabed, not just floating shelf ice breaking off at the edges.
The numbers were stark. After the landfast sea ice broke out, Hektoria experienced roughly a six-fold speedup in ice flow and an approximately forty-fold increase in its thinning rate. The sharpest single episode, 8.2 plus or minus 0.2 kilometers of retreat, occurred between November and December 2022. The researchers attributed the collapse to a mechanism they call ice plain calving: a buoyancy-driven process in which lightly grounded ice thins from below until it floats free and disintegrates.
Laser altimetry from NASA’s ICESat-2 satellite added a vertical dimension to the picture. The ATL06 Version 6 land-ice-height dataset showed that the glacier’s surface continued to drop through the Antarctic winter of 2022, even after major calving episodes had paused. That pattern pointed to sustained melt at the glacier’s base rather than surface processes alone, suggesting warm water was still at work beneath the ice even during the coldest months.
What scientists still do not know
For all the precision of the satellite measurements, several critical pieces remain missing. No direct ocean-temperature readings tied to the January 2022 sea-ice breakout have been published. Researchers infer that warm water reached the glacier’s base because the thinning and speedup patterns match basal-melt signatures, but without hydrographic observations from beneath the ice, the exact thermal forcing that drove the melt rate is an estimate, not a direct measurement.
The ICESat-2 data confirm that the glacier’s surface dropped through the 2022 winter, but specific elevation-change values and error bars for that critical period have not been numerically extracted in any publicly available analysis. The thinning signal is visible in the gridded datasets, yet its precise magnitude during the months between calving episodes has not been reported with the same confidence as the retreat distances. That gap makes it harder to determine exactly how quickly the ice plain transitioned from grounded to floating.
A larger question looms over the region: whether the landfast sea ice will reform. If it does not, the remaining grounded ice at Hektoria and Green faces continued exposure to ocean swell and warm-water intrusion. The Nature Geoscience study’s mechanism implies that any lightly grounded ice plain in the embayment could undergo the same buoyancy-driven calving sequence once it thins enough. But predicting sea-ice formation years in advance involves atmospheric and oceanic variables that current models handle with significant uncertainty, and no published forecast commits to a timeline for the next major retreat.
What Hektoria tells us about the rest of Antarctica
It is tempting to extrapolate from Hektoria to the continent’s largest and most consequential glaciers, particularly Thwaites and Pine Island in West Antarctica, which between them hold enough ice to raise global sea levels by more than a meter. But glaciologists urge caution. Hektoria’s geometry made it unusually vulnerable: a shallow ice plain, already thinned by 20 years of post-Larsen B adjustment, sitting behind a sea-ice barrier that turned out to be temporary. Thwaites and Pine Island operate under different constraints, with deeper beds, different ocean circulation patterns, and distinct ice-shelf configurations.
What Hektoria does demonstrate, with unusual clarity, is the mechanism by which warm ocean water can dismantle grounded ice far more rapidly than surface melting alone. The record-setting label applies specifically to the speed of grounded ice retreat, not necessarily to total ice volume lost or direct sea-level contribution, which for Hektoria is relatively modest compared to the continent’s giant glaciers. But the physical process, warm water thinning ice from below until it lifts off the seabed and breaks apart, is not unique to this one glacier. It is the same process that concerns researchers studying ice loss across West Antarctica and parts of East Antarctica.
As of June 2026, the Larsen B embayment remains under close satellite surveillance. Whether the landfast sea ice returns, and how Hektoria’s remaining grounded ice responds if it does not, will test whether the 2022 collapse was a singular event or the opening chapter of a longer unraveling along the Antarctic Peninsula.
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*This article was researched with the help of AI, with human editors creating the final content.
