Ocean water is pushing miles beneath Antarctica’s “Doomsday Glacier,” making it more vulnerable to melting than previously thought, according to new research that used radar data from space to create an X-ray of the crucial glacier.
As the salty, relatively warm ocean water meets the ice, it causes a “powerful melt” under the glacier and could mean that global sea level rise predictions are underestimated, according to the study published Monday in the Proceedings of the National Academy of Sciences.
West Antarctica’s Thwaites Glacier – nicknamed the “Doomsday Glacier” because its collapse could cause catastrophic sea level rise – is the widest glacier in the world and about the size of Florida. It is also Antarctica’s most fragile and unstable glacier, largely because the land it lies on slopes downward, allowing ocean water to eat away at the ice.
Thwaites, which already contributes 4% to global sea level rise, contains enough ice to raise sea levels by more than 60 cm. But because it also acts as a natural dam for the surrounding ice in West Antarctica, scientists estimate that its complete collapse could ultimately lead to a sea level rise of about 3 meters – a catastrophe for the world’s coastal communities.
Many studies have pointed out Thwaites’ enormous vulnerabilities. Global warming, caused by humans’ burning of fossil fuels, is leaving the Earth ‘hanging by its fingernails’, a 2022 study found.
This latest investigation adds a new and alarming factor to the projections of 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 last year to create an X-ray of the glacier. This allowed them to paint a picture of changes in Thwaites’ ‘grounding line’, the point at which the glacier rises from the seabed and becomes a floating ice shelf. Grounding lines are vital to the stability of ice sheets and are a key point of vulnerability for Thwaites, but are difficult to study.
“In the past, we only had sporadic data to look at this,” said Eric Rignot, professor of Earth system sciences at the University of California, Irvine and co-author of the study. “In this new dataset, used daily and over several months, we have solid observations of what is going on.”
They watched as the seawater penetrated many kilometers under the glacier and then moved out again, following the daily rhythm of the tides. When the water rushes in, it is enough to “lift the glacier’s surface by inches,” Rignot told CNN.
He suggested that the term “grounding zone” may be more appropriate than the grounding line because, according to their research, it can travel nearly 4 miles in a twelve-hour tidal cycle.
The speed of the seawater, which moves significant distances in a short time, increases the melting of the glaciers because once the ice melts, freshwater is washed away and replaced by warmer seawater, Rignot said.
“This process of widespread, massive seawater intrusion will increase predictions of sea level rise 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 finding provides a process that has not yet been included in models,” he told CNN. And while these results only apply to certain parts of the glacier, he said, “this could accelerate the rate of ice loss in our forecasts.”
One uncertainty that needs to be unraveled is whether the flow of seawater under Thwaites is a new phenomenon or whether it is significant but long unknown, says James Smith, a marine geologist at the British Antarctic Survey, who was not involved in the study.
“Either way, it is clearly an important process that needs to be integrated into ice sheet models,” he told CNN.
Noel Gourmelen, professor of Earth Observation at the University of Edinburgh, said the use of radar data for this research was interesting. “Ironically, by going to space, using our growing satellite capabilities, we are learning a lot more about this environment,” he told CNN.
There are still many uncertainties about what the study’s findings mean for Thwaites’ future, said Gourmelen, who was not involved in the study. It is also unclear how widespread this process is around Antarctica, he told CNN, “although it is very likely it is happening elsewhere as well.”
A regime change
Antarctica, an isolated and complex continent, appears increasingly vulnerable to the climate crisis.
By analyzing satellite data and using climate models, they found that this record level “would have been highly unlikely without the influence of climate change.”
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 around Antarctica last year.
Melting sea ice doesn’t directly affect sea level rise because it’s already floating, but it does expose ice caps and coastal glaciers to waves and warm ocean water, making them much more vulnerable to melting and fall apart.
The researchers also used climate models to predict the potential speed of recovery after such extreme sea ice loss and found that even after 20 years, not all the ice will return.
“The consequences of Antarctic sea ice remaining low for more than 20 years would be profound, including on local and global weather,” Louise Sime, co-author of the BAS study, said in a statement.
The findings add to evidence in recent years that the region is facing “lasting regime change,” the authors wrote.
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