Ocean water is advancing miles below Antarctica’s “Doomsday Glacier” making it more vulnerable to melting than previously thought, according to new research that used radar data from space to X-ray the crucial glacier.
As relatively warm, salty ocean water meets the ice, it is causing “vigorous melting” beneath the glacier and could mean global projections of sea level rise are being underestimated, according to study published Monday in the journal Proceedings of the National Academy of Sciences.
The Thwaites Glacier in West Antarctica – nicknamed the “Doomsday Glacier” because it is Collapse could cause catastrophic rise in sea levels – is the widest glacier in the world and is approximately the size of Florida. It is also the most vulnerable and unstable glacier in Antarctica, largely because the land on which it sits slopes downward, allowing ocean waters to erode its ice.
Thwaites, which already contributes 4% to global sea level rise, contains enough ice to raise sea levels by more than 60 centimeters. But because it also acts as a natural dam for the surrounding ice in West Antarctica, scientists estimated its total collapse could lead to a rise in sea levels of around 3 meters – a catastrophe for the world’s coastal communities.
Many studies have pointed to Thwaites’ immense vulnerabilities. Global warming, driven by the burning of fossil fuels by humans, has left it hanging “by the nails”, according to a 2022 study.
This latest research adds a new and alarming factor to projections of its fate.
A team of glaciologists – led by scientists at the University of California, Irvine – used high-resolution satellite radar data, collected between March and June of last year, to create an X-ray of the glacier. This allowed them to build a picture of changes in the Thwaites “grounding line,” the point at which the glacier rises from the sea floor and becomes a floating ice shelf. Grounding lines are vital to the stability of ice sheets and a key point of vulnerability for Thwaites, but they have been difficult to study.
“In the past, we only had sporadic data to analyze this,” said Eric Rignot, professor of Earth system science at the University of California, Irvine and co-author of the study. “In this new dataset, daily and over several months, we have solid observations of what is happening.”
They watched the sea water pass beneath the glacier for many kilometers and then emerge again, following the daily rhythm of the tides. When the water enters, it is enough to “raise” the surface of the glacier by centimeters, Rignot told CNN.
He suggested that the term “grounding zone” might be more appropriate than grounding line, as it can move nearly 4 miles in a 12-hour tidal cycle, according to his research.
The speed of seawater, which travels considerable distances in a short period of time, increases glacier melting because as soon as the ice melts, freshwater is eliminated and replaced by warmer seawater, Rignot said.
“This process of widespread and massive seawater intrusion will increase projections of sea level rise in Antarctica,” he added.
Ted Scambos, a glaciologist at the University of Colorado at Boulder who was not involved in the study, called the research “fascinating and important.”
“This discovery provides a process that has not yet been taken into account in models,” he told CNN. And although these results only apply to certain areas of the glacier, he said, “this could accelerate the rate of ice loss in our predictions.”
One uncertainty to be unraveled is whether the flow of seawater beneath Thwaites is a new phenomenon or whether it is significant but long unknown, said James Smith, a marine geologist at the British Antarctic Survey who was not involved in the study.
“Either way, it’s clearly an important process that needs to be incorporated into ice sheet models,” he told CNN.
Noel Gourmelen, professor of Earth observation at the University of Edinburgh, said using radar data for this study was interesting. “Ironically, it is by going into space, using our growing satellite capabilities, that we are learning so much more about this environment,” he told CNN.
There are still many unknowns about what the study’s findings mean for Thwaites’ future, said Gourmelen, who was not involved in the research. It’s also unclear how widespread this process is around Antarctica, he told CNN, “although it’s highly likely that this is happening elsewhere as well.”
A regime change
Antarctica, an isolated and complex continent, appears to be increasingly vulnerable to the climate crisis.
In a separate study, also published on Monday, researchers from the British Antarctic Survey looked at the reasons for the record low levels of sea ice surrounding Antarctica last year.
Analyzing satellite data and using climate models, they found that this record value would have been “extremely unlikely to happen without the influence of climate change”.
Melting sea ice does not directly affect sea level rise because it is already floating, but it leaves coastal ice sheets and glaciers exposed to waves and warm ocean waters, making them much more vulnerable to melting and rupture.
The researchers also used climate models to predict the potential speed of recovery from such an extreme loss of sea ice and found that even after two decades, not all of the ice will return.
“The impacts of low Antarctic sea ice remaining for more than twenty years would be profound, including on local and global climate,” said Louise Sime, co-author of the BAS study, in a statement.
The findings add to evidence over the past few years that the region faces “lasting regime change,” the authors wrote.
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