New NASA-funded research warns that because of human-caused global heating, West Antarctica's massive Thwaites Glacier is at risk of reaching a tipping point that could raise the global sea level by about 20 inches.
"After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years. That would make for a sea level rise of about half a meter (1.64 feet)."
—Hélène Seroussi, NASA
The study, published Monday in the journal the Proceedings of the National Academy of Sciences, was conducted by researchers at the Georgia Institute of Technology, NASA Jet Propulsion Laboratory, and the University of Washington.
Though this team focused on the Thwaites Glacier—which is about the size of Florida or Britain—the report follows several others that have raised alarm about how rapidly ice is disappearing in Antarctica, including one study from May which found that the continent's ice sheets are thinning five times faster than they were in the 1990s.
In a statement Monday, Georgia Tech explained that researchers found "instability hidden within Antarctic ice is likely to accelerate its flow into the ocean and push sea level up at a more rapid pace than previously expected."
In the last six years, five closely observed Antarctic glaciers have doubled their rate of ice loss, according to the National Science Foundation. At least one, Thwaites Glacier, modeled for the new study, may be in danger of succumbing to this instability, a volatile process that pushes ice into the ocean fast.
The Thwaites Glacier is often called "one of the world's most dangerous glaciers" because of its potential contributions to sea level rise. As Common Dreams reported in January, NASA scientists recently discovered a 1,000-foot deep cavity in the glacier large enough to have held about 14 billion tons of ice before it melted, which heightened concerns about the glacier's future.
Researchers behind the new study weren't able to project exactly how much ice the Thwaites Glacier will lose in the next 50 to 800 years, "due to unpredictable fluctuations in climate and the need for more data," but they factored the instability into 500 ice flow simulations for the glacier, which "together pointed to the eventual triggering of the instability," according to the Georgia Tech statement.
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"If you trigger this instability, you don't need to continue to force the ice sheet by cranking up temperatures. It will keep going by itself, and that's the worry," said lead author Alex Robel, an assistant professor in Georgia Tech's School of Earth and Atmospheric Sciences. However, he added, "climate variations will still be important after that tipping point because they will determine how fast the ice will move."
The simulations spanned several centuries, as is common for studies on sea level rise. The models suggested that the glacier could reach the tipping point "in the next 200 to 600 years," said co-author and NASA scientist Hélène Seroussi. "It depends on the bedrock topography under the ice, and we don't know it in great detail yet."
"There's almost eight times as much ice in the Antarctic ice sheet as there is in the Greenland ice sheet and 50 times as much as in all the mountain glaciers in the world."
—Alex Robel, Georgia Tech
"After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years," Seroussi said. "That would make for a sea level rise of about half a meter (1.64 feet)."
Experts have also raised alarm about how quickly ice is melting in Greenland and the Arctic, but Antarctica is of particular concern because, as Robel pointed, "there's almost eight times as much ice in the Antarctic ice sheet as there is in the Greenland ice sheet and 50 times as much as in all the mountain glaciers in the world."
While the researchers acknowledged the need for further study, they also emphasized the importance of preparing for rising seas—which increasingly endanger island nations and coastal communities.
"You want to engineer critical infrastructure to be resistant against the upper bound of potential sea level scenarios a hundred years from now," said Robel. "It can mean building your water treatment plants and nuclear reactors for the absolute worst-case scenario, which could be two or three feet of sea level rise from Thwaites Glacier alone, so it's a huge difference."