A sudden, record-breaking glacier collapse in Antarctica is revealing how unseen forces beneath the ice could reshape the planet’s future. Credit: Shutterstock

In a record-breaking event, Antarctica’s Hektoria Glacier lost nearly half its mass in just two months.

A glacier on the eastern side of Antarctica has undergone the fastest retreat ever documented in modern times. In only two months, nearly half of the ice vanished.

According to a new study led by the University of Colorado Boulder and published in Nature Geoscience, the Hektoria Glacier lost about eight kilometers ( 5miles) of ice in early 2023. Researchers found that the glacier’s collapse was driven by its unusually flat bedrock, which allowed it to start floating once it thinned significantly. This shift set off a rapid and uncommon calving event that caused the glacier to break apart.

The discovery offers scientists a new way to pinpoint glaciers that may be at risk of similar rapid retreats. Although Hektoria Glacier covers just 115 square miles (about the size of Philadelphia), experts warn that comparable events on larger Antarctic glaciers could have severe consequences for global sea level rise.

Witnessing the Aftermath

“When we flew over Hektoria in early 2024, I couldn’t believe the vastness of the area that had collapsed,” said Naomi Ochwat, lead author and CIRES postdoctoral researcher. “I had seen the fjord and notable mountain features in the satellite images, but being there in person filled me with astonishment at what had happened.”

Hektoria Glacier on Antarctica’s Eastern Peninsula experienced the fastest retreat recorded in modern history—in just two months, nearly 50 percent of the glacier disintegrated. This video illustrates how and why Hektoria Glacier retreated so rapidly in late 2022 and early 2023. New CU Boulder-ledresearch shows the main driver was underlying flat bedrock that enabled the glacier to go afloat after it substantially thinned, causing a rare rapid calving process. Credit: Lauren Lipuma/CIRES

The research team, which included CIRES Senior Research Scientist Ted Scambos, had been studying the region around Hektoria Glacier using satellite imagery and remote sensing for an unrelated project. Their goal was to investigate why sea ice had detached from a nearby glacier roughly ten years after an ice shelf collapse in 2002. During this analysis, lead author Naomi Ochwat discovered surprising data showing that Hektoria had almost completely vanished within just two months.

Determined to find out what caused such an abrupt change, she began a new investigation to uncover why the glacier retreated so rapidly.

The Role of Ice Plain Topography

Many glaciers in Antarctica are tidewater glaciers—glaciers that rest on the seabed and end with their ice front in the ocean and calve icebergs. The topography beneath these glaciers is often varied; they may sit upon deep canyons, underground mountains, or big flat plains. In Hektoria’s case, the glacier rested on top of an ice plain, a flat area of bedrock below sea level. Researchers previously found that 15,000-19,000 years ago, Antarctic glaciers with ice plains retreated hundreds of meters per day, and this helped the team better understand Hektoria’s rapid retreat.

When tidewater glaciers meet the ocean, they can go afloat, where they float on the ocean’s surface rather than resting on solid ground. The point at which a glacier goes afloat is called the grounding line. Using several types of satellite data, the researchers discovered Hektoria had multiple grounding lines, which can indicate a glacier with ice plain topography underneath.

Hektoria’s ice plain caused a large part of the glacier to go afloat suddenly, causing it to calve quickly. Going afloat exposed it to ocean forces that opened up crevasses from the bottom of the glacier, eventually meeting crevasses exposed from the top, causing the entire glacier to calve and break away.

Tracking the Rapid Retreat

The team used satellite data to study the glacier at different time intervals and created a robust picture of the glacier, its topography, and its retreat.

“If we only had one image every three months, we might not be able to tell you that the glacier lost two and a half kilometers in two days,” Ochwat said. “Combining these different satellites, we can fill in time gaps and confirm how quickly the glacier lost ice.”

The researchers also used seismic instruments to identify a series of glacier earthquakes at Hektoria that occurred simultaneously with the rapid retreat period. The earthquakes confirmed the glacier was grounded on bedrock rather than floating, proving both the presence of an ice plain topography and that the ice loss contributed directly to global sea level rise.

Ice plain topographies have been detected across numerous glaciers in Antarctica, and the research on Hektoria will help scientists anticipate and forecast potential rapid retreat across the continent.

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

Reference: “Record grounded glacier retreat caused by an ice plain calving process” by Naomi Ochwat, Ted Scambos, Robert S. Anderson, J. Paul Winberry, Adrian Luckman, Etienne Berthier, Maud Bernat and Yulia K. Antropova, 3 November 2025, Nature Geoscience. DOI: 10.1038/s41561-025-01802-4

Never miss a breakthrough: Join the SciTechDaily newsletter. Follow us on Google, Discover, and News.