Rapidly melting Greenland’s ice sheet will eventually raise sea levels by at least 27 centimeters (10.6 inches), more than double previous predictions, according to a study released Monday.
It’s because of something that could be called zombie ice cream. It is doomed ice which, while still attached to thicker areas of ice, is no longer replenished by parent glaciers which now receive less snow. Without replenishment, the doomed ice is melting due to climate change and will inevitably cause seas to rise, said study co-author William Colgan, a glaciologist at the Geological Survey of Denmark and Greenland.
“It’s dead ice. It will just melt and disappear from the ice cap,” Colgan said in an interview. “That ice has been relegated to the ocean, no matter what climate (emissions) scenario we take now.”
The study’s lead author, Jason Box, a glaciologist with the Greenland Survey, said it was “more than a foot in the grave”.
The unavoidable ten inches in the study is more than double the sea level rise scientists previously expected from the melting Greenland ice sheet. The study published in the journal Nature Climate Change indicates that it could reach up to 30 inches (78 centimeters). By contrast, last year’s Intergovernmental Panel on Climate Change report predicted a range of 2 to 5 inches (6 to 13 centimeters) for likely sea level rise from melting. of Greenland ice by 2100.
What the scientists did for the study was look at the ice in equilibrium. In perfect balance, snowfall in the mountains of Greenland drains, recharges and thickens the flanks of glaciers, balancing out what melts at the edges. But in recent decades there has been less replenishment and more melting, creating an imbalance. The study authors looked at the ratio of what is added to what is lost and calculated that 3.3% of Greenland’s total ice volume will melt no matter what happens with the global reduction in pollution. by carbon, Colgan said.
“I think starving would be a good expression,” for what happens to the ice cream, Colgan said.
One of the study’s authors said more than 110 trillion metric tons (120 trillion tonnes) of ice is already doomed to melt because of the ice sheet’s inability to replenish its edges. When this ice melts into the water, if it were concentrated just over the United States, it would be 11 meters (37 feet) deep.
The numbers are a global average for sea level rise, but some places farther from Greenland would get more and places closer, like the east coast of the United States, would get less. While 10.6 inches might not seem like a lot, it would be beyond high tides and storms making them even worse, so this sea level rise “will have huge societal, economic and environmental impacts” , said Ellyn Enderlin, professor of geosciences. at Boise State University, which was not part of the study.
“This is a very significant loss and will have a detrimental effect on coasts around the world,” said NYU’s David Holland, who just returned from Greenland but is not part of the study.
This is the first time scientists have calculated a minimum ice loss – and accompanying sea level rise – for Greenland, one of Earth’s two massive ice caps that is slowly shrinking due to climate change due to the burning of coal, oil and natural gas. The scientists used an accepted technique to calculate the minimum committed ice loss, that used on mountain glaciers for the entire frozen giant island.
Pennsylvania State University glaciologist Richard Alley, who was not part of the study but said it made sense, said the committed melting and sea level rise are like an ice cube placed in a cup of hot tea in a warm room.
“You have lost mass to the ice,” Alley said in an email. “Similarly, most of the world’s mountain glaciers and the edges of Greenland would continue to lose mass if temperatures were stabilized at modern levels, because they were placed in warmer air, just like your ice cube was put in hotter tea.”
Time is the unknown key here and a bit of a problem with the study, said two outside scientists, Leigh Stearns of the University of Kansas and Sophie Nowicki of the University at Buffalo. The study’s researchers said they couldn’t estimate when the melting occurred, but in the last sentence they mention “during this century,” without supporting it, Stearns said.
Colgan replied that the team didn’t know how long it would take for all of the doomed ice to melt, but making an educated guess, it would likely be by the end of this century, or at least by 2150.
Colgan said it was actually a best-case scenario. 2012 (and to a different degree 2019) was a huge melt year, when the balance between adding and subtracting ice was most out of balance. If Earth begins to experience more years like 2012, melting Greenland could trigger a sea level rise of 78 centimeters (30 inches), he said. Those two years seem extreme now, but years that seem normal now would have been extreme 50 years ago, he said.
“That’s how climate change works,” Colgan said. “Today’s outliers become tomorrow’s averages.”