Ocean water rushes miles under ‘doomsday glacier’ with potentially dire implications for sea level rise

CNN
—

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 take an X-ray image of the key glacier.

When salty, relatively warm ocean water meets the ice, it causes “vigorous melting” beneath the glacier and can average estimates of global sea level rise are underway according to a 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 is roughly the size of Florida. It is also Antarctica’s most vulnerable and unstable glacier, in large part because the land it sits on slopes downward, allowing ocean waters to eat away at its ice.

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

Many studies have pointed 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 alarming factor to the projections of its 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 image of the glacier. This allowed them to build a picture of changes in Thwaites’ “grounding line”, the point at which an iceberg rises from the sea floor to become a floating ice shelf. Ground wires are vital to the stability of the ice sheets and are a key point of vulnerability for Thwaites, but they have been difficult to study.

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

They watched seawater push under the glacier for many miles and then recede again according to the daily rhythm of the tides. When the water flows in, it only “raises” the surface of the glacier by inches, Rignot told CNN.

He suggested that the term “grounding zone” may be more accurate than grounding line because it can move nearly 4 miles during 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 the ice melts, fresh water is washed away and replaced by warmer seawater, Rignot said.

“This process of large-scale, 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 finding provides a process not yet accounted for in models,” he told CNN. And while these results only apply to certain areas of the glacier, he said, “this could accelerate the rate of ice loss in our predictions.”

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

“In any case, it’s clearly an important process to incorporate 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 the study was interesting. “The irony is that by 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 the future of Thwaites, said Gourmelen, who was not involved in the research. It’s also unclear how widespread the process is around Antarctica, he told CNN, “although it’s highly likely that it’s happening elsewhere.”

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

In a separate study, also published on Monday, scientists from the British Antarctic Survey looked at the reasons for the record low level of sea ice around Antarctica last year.

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

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

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

“The impacts of Antarctic sea ice remaining low for more than twenty 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 over the past several years that the region is facing “permanent regime change,” the authors wrote.