Global warming is linked to rapid melting of the massive West Antarctic Ice Sheet, which could cause sea levels to rise more than 10 feet in coming centuries.
The collapse is irreversible, according to two new studies that report on the melting.
“It has passed the point of no return,” said Eric Rignot, a glaciologist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of one of the studies published in Geophysical Research Letters. “The retreat of ice in that sector is unstoppable.”
If that retreat continues, the entire West Antarctic Ice Sheet could eventually melt into the ocean and raise sea levels.
“More or less, the rise from WAIS here will be comparable to the Hurricane Sandy storm surge,” said Richard Alley, professor of geosciences at Pennsylvania State University. “Except WAIS’ water will stay, and get all the coasts.”
Scientists linked the melting to climate change caused by human use of fossil fuels that emit greenhouse gases.
Researchers focused on the glaciers in the Amundsen Sea sector, an area long referred to as the weak underbelly of West Antarctica. Due to multiple factors including warming oceans and the depletion of the ozone in that area, ice melt is quickly increasing.
In West Antarctica, unlike the eastern part of the continent, most of the ice mass lies below the water. Beneath the surface where glaciers detach from the land is what scientists call the “grounding line.” This line has been retreating at record speeds in recent years.
This is because the thawing glacier creates a vicious cycle. The more it melts, the further inland the grounding line retreats into the continent where the ice is thicker.
Thicker ice at the grounding line means more rapid melting, said Sridhar Anandakrishnan, a professor of geosciences at Penn State. More ice is exposed to the warming ocean waters, speeding up the flow, causing the glacier to retreat further inland to even thicker ice and so on and so forth.
“Even if the ocean is not warming up…the system is sort of a chain reaction that is unstoppable,” Rignot said. “Every process of retreat feeding the next one.”
There isn’t any evidence to suggest ocean temperatures will stop increasing either as the planet continues to warm; more likely, waters will only get hotter.
If the glaciers only in the Amundsen Sea sector melt, they will raise sea levels by 4 feet, according to his study, done by NASA and the University of California, Irvine.
“You’ve added water to a finite space,” Anandakrishnan said, “and the water’s gonna go up.”
If it continues to melt at this pace, the entire sector could flow into the ocean in the next two centuries, according to Rignot, although it could take less or more time.
The second study, lead by Ian Joughin of the University of Washington, focused on the Thwaites glacier and used computer modeling to determine that the glacier’s retreat is rapidly accelerating.
Science published the study online on Monday.
Since the ice sheet is interconnected, melting of the Thwaites glacier will likely lead to a collapse of most or all of West Antarctica, said Alley, a prominent climate change scientist who is not associated with the studies.
This would cause sea levels to rise at least 10 feet in the next century or two, according to the study.
One reason the retreat is irreversible is because there is no physical barrier to stop the glaciers, like a large hill or mountain.
“We are fairly confident that there is no such hill,” Rignot said.
These findings, if confirmed by more research, could increase the Intergovernmental Panel on Climate Change’s sea level projections.
“The IPPC numbers for 2100 will almost certainly be revised and revised upwards,” Anandakrishnan said. The current IPCC already predicts extreme weather, droughts and human displacement due to climate change.
However, Alley noted that the results don’t drastically change projections for this century since major retreat is further in the future, and that we should focus on salvageable ice.
“If we have committed to 3 meters or so of globally averaged sea-level rise from West Antarctica, even if delayed by many centuries, the costs are sobering, but are not as high as the costs of also committing to loss of Greenland’s ice and parts of East Antarctica’s ice,” Alley said. “While some additional shrinkage of Greenland probably is already committed, major loss in Greenland and East Antarctica is not guaranteed yet.
Originally published by Medill Reports Chicago