Antarctica’s Hectoria Glacier experienced an astonishing collapse from early 2022 to spring 2023, receding at a pace rarely seen in modern observations. In just 15 months, the glacier’s length has decreased by about 25 kilometers (15 miles). During a particularly dramatic two-month period, the glacier terminus retreated more than eight kilometers, marking the fastest retreat of ground-based glacier ice ever recorded in modern history.
Scientists recently analyzed this phenomenon using multiple types of remote sensing data and concluded that the shape and structure of the glacier played a major role in its rapid collapse. Hectoria Glacier, located on the Antarctic Peninsula, begins on land and extends into the ocean, with its outer portion forming a mass of floating ice known as the “tongue of ice.” The researchers found that the glacier lost not only this floating tongue of ice, but also much of the grounded ice that was on flat areas of the bedrock. Land ice loss directly contributes to sea level rise.
Although Hectoria is relatively small compared to some of Antarctica’s giant glaciers, scientists warn that similar processes affecting larger glaciers could have a much larger impact around the world.
Record of glacier retreat photographed from space
Satellite images reveal massive amounts of ice loss from the Hectoria Glacier in the eastern Antarctic Peninsula. The latest clear Landsat images covering the entire area were taken about a year after the dramatic retreat occurred, as cloud-free images from March of the previous year were not available.
The Hectoria terminus remained largely stable after the sudden retreat, while nearby Green Glacier continued to shrink, according to the study.
The story behind Hectoria’s collapse actually began more than 20 years ago. In 2002, the Larsen B ice shelf rapidly fractured and collapsed. The ice shelf acted as a barrier to stabilize Hectoria and nearby glaciers. After the glaciers disappeared, over the next several years, the glaciers in the area began to thin and retreat.
By 2011, land sea ice in Larsen B Bay near the Hectoria terminus had expanded enough to provide temporary support, allowing the glacier to slowly advance again.
Loss of sea ice causing rapid collapse
That stability didn’t last long. In January 2022, the sea ice on land in the bay suddenly broke apart. This is likely due to strong ocean swells that destabilized the area. Once that support disappeared, Hectoria Glacier quickly began changing again.
During the austral summer, the floating tongue of ice steadily broke apart due to repeated calving events, leading to a retreat of about 16 kilometers.
The glacier briefly stabilized during the austral winter of 2022. But satellite laser measurements, including data from NASA’s ICESat-2 (Ice, Cloud, and Land Elevation Satellite-2) mission, show that the glacier continued to thin beneath the surface during that time.
Scientists identify ice loss due to buoyancy
Researchers later determined that the remaining ice was still on the surface during the austral spring of 2022, based on earthquakes detected beneath the glacier. According to their analysis, the ice existed across large, relatively flat sections of rock known as ice plains.
In this type of terrain, seawater moves beneath the glacier during high tide, temporarily lifting some of the ice off the ground. When the ice becomes thin enough, large pieces can suddenly break off and break off all at once.
Scientists believe this process, known as buoyancy-induced differentiation, triggered the second phase of the glacier’s retreat. During that stage, Hectoria lost another eight kilometers of distance.
NASA satellites could help track future glacier collapses
“New platforms developed by NASA and partners, such as the NISAR and SWOT satellites, can help us understand rapid changes in glaciers.”
Naomi Oshwat, a glaciologist at the University of Innsbruck and lead author of the study, is now investigating whether other glaciers may face similar risks. As temperatures continue to rise around the Antarctic Peninsula, more glaciers are losing their protective ice tongues and becoming tidal glaciers. This means that the terminus of the glacier lies directly on the ocean floor. This type of glacier is also common in Alaska and Greenland.
Oshwat and study co-author Ted Scambos, a senior research scientist at the University of Colorado Boulder, said new satellite technology could significantly improve scientists’ understanding of the rapid retreat of glaciers.
For example, the NISAR (NASA-ISRO Synthetic Aperture Radar) satellite can measure movement over land and ice surfaces with centimeter precision. Mr Scambos said the observations were “very useful for assessing the structure of Hectoria and other glaciers in the region”.
“In addition to NISAR,” Oshwat added. “We are particularly interested in learning what SWOT can tell us about rapid changes in glaciers.”
SWOT (Surface Water and Ocean Topography) satellites were designed primarily to measure detailed changes in Earth’s water surface. Scientists are currently studying how it can be used to study the cryosphere, including ice shelves and sea ice.
Hectoria Glacier may continue its gradual retreat
Scientists believe that the most dramatic phase of the Hectorian glacier collapse may already be over. Future retreat is expected to continue more slowly as glacier mass and elevation decrease.
Scambos said he wouldn’t be surprised if glacier movement continues to slow in the coming years.
“The glaciers have lost so much altitude and mass that it is impossible to continue to maintain the same production,” he said. “It’s becoming a fjord instead of a glacier.”
