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Ocean water is pushing miles beneath Antarctica’s “doomsday glacier,” making it more vulnerable to melting than previously thought, according to new research that uses radar data from space to take an X-ray of the crucial glacier.

As salty, relatively warm ocean water meets the ice, it causes “vigorous melting” beneath the glacier and can projections of average global sea level rise are underestimated, according to the study, published Monday in the Proceedings of the National Academy of Sciences.

The Thwaites Glacier in West Antarctica – nicknamed the “Doomsday Glacier” because its collapse could cause a catastrophic rise in sea levels – is the widest glacier in the world and about the size of Florida. It is also Antarctica’s most vulnerable and unstable glacier, largely because the land it sits on is subsiding, allowing ocean waters to eat away at its ice.

The Thwaites, which already contributes 4% to global sea level rise, contains enough ice to raise sea levels by more than 2 feet. But because it also acts as a natural dam for the surrounding ice in West Antarctica, scientists have estimated that its complete collapse could eventually cause sea levels to rise by about 10 feet — a disaster for coastal communities around the world.

Many studies point to Thwaites’ immense vulnerability. Global warming caused by humans burning fossil fuels has left it hanging “by its fingernails,” according to a 2022 study.

This latest research adds a new and troubling factor to predictions about his fate.

A team of glaciologists led by scientists from the University of California, Irvine, used high-resolution satellite radar data collected between March and June of last year to create an X-ray image of the glacier. This allowed them to build a picture of changes in the Thwaites ‘grounding line’, the point where the glacier rises from the sea floor and becomes a floating ice shelf. Grounding lines are vital to the stability of the ice sheets and a key point of vulnerability for the Thwaites, but they are difficult to study.

“In the past, we’ve only had sporadic data to look at this,” said Eric Rignot, professor of Earth system science at UC Irvine and co-author of the study. “In this new data set, which is daily and over several months, we have solid observations of what’s going on.”

They watched as seawater was forced under the glacier for many miles and then released again, following the daily rhythm of the tides. When the water flows, it’s enough to “raise” the surface of the glacier by centimeters, Rigneault told CNN.

He suggested that the term “grounding zone” might be more appropriate than grounding line because it can move nearly 4 miles in a 12-hour tidal cycle, according to their research.

The speed of seawater moving significant distances in a short period of time increases the melting of glaciers because as soon as the ice melts, the freshwater is washed away and replaced by warmer seawater, Rigneault said.

“This process of widespread, massive seawater intrusion will increase sea level rise projections from Antarctica,” he added.

Ted Scambos, a glaciologist at the University of Colorado Boulder who was not involved in the study, called the research “fascinating and important.”

“This discovery provides a process that has not yet been included in models,” he told CNN. And although these results only apply to certain areas of the glacier, he said, “this may speed up the rate of ice loss in our projections.”

One uncertainty that needs to be resolved is whether the surge of seawater under Thwaites is a new phenomenon or has been significant but unknown for a long time, said James Smith, a marine geologist with the British Antarctic Survey who was not involved in the study.

“Either way, it’s clearly an important process that needs to be included in ice sheet models,” he told CNN.

Noel Gurmelen, Professor of Earth Observation at the University of Edinburgh, said the use of radar data for this research was interesting. “Ironically, going into space, using our growing satellite capabilities, we’re learning a lot more about that environment,” he told CNN.

There are still many unknowns about what the study results mean for Thwaites’ future, said Gurmelen, who was not involved in the research. It’s also unclear how widespread this process is around Antarctica, he told CNN, “although it’s very likely that it’s happening elsewhere.”

Antarctica, an isolated and complex continent, appears increasingly vulnerable to the climate crisis.

Analyzing satellite data and using climate models, they found that this record low would be “extremely unlikely to occur without the influence of climate change.”

In a separate study, also published on Monday, researchers from the British Antarctic Survey looked at the causes of record low sea ice levels around Antarctica last year.

Melting sea ice does not directly affect sea level rise because already floating but leaves coastal ice sheets and glaciers exposed to waves and warm ocean waters, making them much more vulnerable to melting and breaking up.

The researchers also used climate models to predict the potential rate of recovery from such extreme sea ice loss and found that even after two decades, not all of the ice will return.

“The impact of Antarctic sea ice remaining low for more than twenty years would be profound, including on local and global weather,” Louise Syme, co-author of the BAS study, said in a statement.

The findings add to evidence over the past few years that the region is facing “permanent regime change,” the authors write.