Antarctica Shock: Hektoria Glacier Lost Nearly Half Its Ice in Two Months — What It Means for Sea Level Rise

Antarctica’s Hektoria Glacier, about 115 square miles (≈298 km²) — roughly the size of Philadelphia — lost nearly half its ice in just two months (November 2022–January 2023). Researchers led by the University of Colorado Boulder reconstructed the collapse in a new study published in Nature Geoscience, showing how fast retreat and a change from grounded ice to floating ice triggered rapid calving and substantial ice loss.

How the collapse unfolded

Hektoria’s retreat combined several processes that turned a usually slow-moving glacier into a dramatic and rapid source of ice loss. The glacier sits on a relatively flat bedrock area called an ice plain. As Hektoria retreated, parts of the ice lost contact with the seafloor and began to float — a transition scientists call “going afloat.” Once afloat, ocean currents and waves attacked the glacier from below while surface stresses opened fractures from above. Where those cracks met, large sections calved away, producing a chain reaction that removed nearly half the glacier’s mass.

Discovery and observations

The event was noticed by researchers studying the nearby Larsen B region. By combining imagery from multiple satellites and seismic records, the team tracked striking short-term motion — about 2.5 km in just two days — and broader loss across the two-month period (roughly 5 miles or ~8 km of ice removed overall). Seismic stations recorded strong signals known as “glacier earthquakes,” confirming massive ice detachments and indicating the glacier had been grounded on bedrock before the collapse. Grounded ice that ends up in the ocean directly increases global sea levels.

“Hektoria’s retreat is a bit of a shock — this kind of lightning-fast retreat really changes what’s possible for other, larger glaciers on the continent,” said Ted Scambos, senior research scientist at CIRES. “If the same conditions set up in some of the other areas, it could greatly speed up sea level rise from the continent.”

Why this matters

Ice-plain topography like Hektoria’s exists beneath several much larger Antarctic glaciers. The new study shows that when these ice plains are exposed and ice goes afloat, the mechanics can produce extremely rapid retreat and large-scale calving. If larger glaciers with comparable geometry were to undergo the same process, the potential contribution to global sea-level rise would be substantial.

On-the-ground perspective

Lead author Naomi Ochwat, a CIRES postdoctoral researcher, said seeing the collapsed fjord firsthand in early 2024 brought home the scale of the loss: satellite imagery had suggested the changes, but flying over the area revealed the full extent of the collapse and the new landscape carved by the retreat.

The Hektoria event is a stark reminder that even long-stable regions of Antarctica can become vulnerable to rapid change when specific conditions align. Continued monitoring with satellites, airborne surveys, and seismic networks is essential to detect similar fast retreats and to better predict future sea-level contributions from the Antarctic Ice Sheet.

Reporting: Study led by University of Colorado Boulder; analysis published in Nature Geoscience. Jennifer Gray is a weather and climate writer for weather.com.