A team at the University of Colorado Boulder identified a process that caused a glacier in Antarctica to retreat faster than any other grounded glacier ever recorded, researchers said, losing about half of its mass in just two months.
After monitoring glaciers in Antarctica, CU Boulder Research Affiliate Naomi Ochwat noticed that the Hektoria Glacier had retreated faster than anything she had ever seen or read about. The grounded glacier, meaning it’s grounded or resting on bedrock, retreated approximately 15.5 miles between January 2022 and March 2023, according to the study. Ochwat set out to understand how and why the Hektoria Glacier retreated so quickly.
“This process, if it could occur on a much larger glacier, then it could have significant consequences for how fast the ice sheet can change as a whole, and other kinds of destabilizing mechanisms could ensue,” Ochwat said. “That could be problematic (for sea level rise).”
The Hektoria Glacier is relatively small by Antarctica standards, about 8 miles across and 20 miles long, CU Boulder Senior Research Scientist Ted Scambos said. The impact on sea level rise from the glacier’s retreat is tiny, equating to fractions of a millimeter.
“But because it reveals a process that occurs during glacial retreat, we’re interested in knowing what other areas of Antarctica, if they should reach this point, with this sort of geometry, what other areas might retreat very rapidly,” Scambos said.
Fast ice, ice named for how it fastens to the coastline, helped support the Hektoria Glacier. Specifically, it helped support Hektoria’s ice tongue, which is ice that protrudes into the water and floats. With warmer conditions, that thin layer of fast ice broke away, and the glacier’s floating ice tongue started to crumble away into the ocean, Scambos said.
That is not an unusual process. What was unprecedented, the scientists found, was what happened to the Hektoria Glacier as it rested on top of its ice plain, which is a flat area of bedrock below sea level. As the incoming water thinned the glacier further, the ice resting on the bedrock rose, and water pushed underneath it, and the resulting pressure caused large slabs of ice to break off. As one slab broke off, more slabs followed, a process Scambos described as similar to dominoes falling over backwards.
“The fact that Hektoria retreated and dumped a bunch of ice into the ocean doesn’t really change much, to be completely honest,” Ochwat said. “The thing that’s important, though, is this mechanism, this ice plain (area) that thins and starts to float and causes a rapid retreat. That process hasn’t been seen before.”
The scientists found that the glacier’s rapid retreat was primarily caused by this ice plain calving process, rather than atmospheric or oceanic conditions. The team used satellite-derived data to study the glacier, such as images and elevation data.
This implies that these types of glaciers resting on ice plains can be easily destabilized, according to the study. Other researchers had previously found that 15,000 to 19,000 years ago, Antarctic glaciers with ice plains retreated hundreds of meters per day, which helped the team better understand Hektoria’s retreat.
Hektoria’s retreat is the fastest retreat for a grounded glacier that’s ever been observed or at least published in research, Scambos said.
“It meant this grounded glacier lost ice faster than any glacier had in the past,” Scambos said. “It’s an important thing to recognize and try to identify various other areas in Antarctica where this process might happen.”
Ice sheets store a tremendous amount of water, which, if released into the ocean, can cause a tremendous increase in sea level rise, Scambos said. In the United States, almost 30% of the population lives in coastal areas, where sea level rise plays a role in flooding, shoreline erosion and hazards from storms, according to the National Oceanic and Atmospheric Administration. Globally, eight of the world’s 10 largest cities are near a coast, according to the U.N. Atlas of the Oceans.
“What happens in Antarctica does not stay in Antarctica, and that’s why it’s really important to research these things because there’s so much we don’t know and so much that could have profound effects for us,” Ochwat said.