Understanding the Potential Threats of Sea Level Rise Caused by Warming Oceans
Antarctica’s “doomsday glacier” — so-called because its collapse could cause catastrophic sea-level rise — is melting rapidly in unexpected ways, according to new research.
The Thwaites Glacier is about the size of Florida and is located in West Antarctica. Part of what holds it in place is an ice shelf that juts out to the surface of the ocean. The shales act as a cork, holding the glacier back on land and providing an important defense against sea level rise.
But the crucial ice shelf is very vulnerable as the ocean warms.
In two studies published Wednesday in the journal Nature, scientists revealed that while the rate of melting beneath much of the ice shelf is slower than previously thought, deep cracks and “staircase” formations in the ice are melting much faster.
As climate change accelerates, the Thwaites Glacier is changing rapidly.
It dumps billions of tons of ice into the ocean each year, contributing about 4% of annual sea level rise. The particularly rapid melting is occurring where the glacier meets the sea floor, which has retreated nearly 14 kilometers since the late 1990s, exposing a larger chunk of ice to relatively warm ocean water.
A complete collapse of Thwaites alone could lead to more than two feet (70 centimeters) of sea level rise, enough to devastate coastal communities around the world. But Thwaites also acts as a natural dam to the surrounding ice in West Antarctica, and scientists estimate that global sea levels could eventually rise by about 10 feet if Thwaites collapses.
Although it may take hundreds or thousands of years, the ice shelf could break up much sooner, triggering a glacier retreat that is unstable and potentially irreversible.
To better understand the reshaping of the remote coastline, a team of American and British scientists from the International Thwaites Glacier Collaboration traveled to the glacier in late 2019.
Using a hot water drill, they drilled a hole nearly 600 meters deep into the ice and sent various instruments over five days to take measurements from the glacier.
The instruments included a torpedo-like robot called the Icefin, which allowed them to access areas that were previously almost impossible to explore. The remotely operated vehicle took pictures and recorded information about water temperature and salinity, as well as ocean currents.
He was able to “swim up to these really dynamic places and get data from the sea floor to the ice,” Britney Schmidt, an associate professor at Cornell University and lead author of one of the papers, told CNN.
The research results reveal “a very nuanced and complex picture,” Peter Davis, an oceanographer with the British Antarctic Survey and lead author of the second paper,
The researchers found that even as the glacier retreated, the rate of melting beneath much of the flat part of the ice shelf was slower than expected. The rate of melting averaged 2 to 5.4 meters per year, according to the study, which is less than previous models predicted.
According to the research, the melting is suppressed by a layer of cooler, fresher water at the base of the glacier, between the ice shelf and the ocean.
“The glacier is still in trouble,” Davis said in a statement, adding, “We found that despite the small amount of melting, the glacier is still retreating rapidly, so there doesn’t seem to be much need to push the glacier out of balance.”
The scientist was also surprised by the second finding. They discovered an undersea glacial landscape far more complex than expected, dominated by strange staircase terraces and fissures – large cracks running through the entire ice shelf.
Melting was particularly rapid in these areas, the research team found. Warm, salty water was able to flow through and widen cracks and crevasses, contributing to instability in the glacier.
“The glacier is not just melting, it’s melting,” Schmidt said.
Melting along the sloping ice of crevasses and terraces “may become the primary trigger for ice shelf collapse,” according to the study’s authors.
The findings add a new layer to a series of alarming studies pointing to the rapid melting of glaciers.
A 2021 study found the ice shelf could break up within the next five years, and last year scientists said the Thwaites Glacier was hanging “by its fingernails” as the planet warms, with the potential for rapid retreat in the coming years.
“We knew these glaciers were changing. We knew it was related to ocean temperature. We knew there was a meltdown. We knew the atmosphere was warming. And we knew the glaciers had broken up,” Schmidt said.
The latest research provides the “missing pieces” to figure out exactly how this change happens, she said.
David Rounce, a glaciologist at Carnegie Mellon University who was not involved in the study, told CNN that the new research offered “new insight into how quickly the bottom of the ice shelf melts and the mechanisms by which it melts, which is very important for improving our understanding and ability to model how Thwaites will change in the future.”
Davis said the research can help create more accurate projections of sea level rise, which can be factored into efforts to mitigate climate change and protect coastal communities. On a more personal note, he said, he also hopes it will make people “sit up and take notice of the changes that are happening.”
“Despite being so far away, the ramifications of what happens at Thwaites will affect everyone,” Davis said.
