Zombie or doomed ice is ice that is still attached to thicker areas of ice, but is no longer fed by those larger glaciers. This is because the parent glaciers receive less replenishment snow. Meanwhile, climate change is melting doomed ice, study co-author said William Colgana glaciologist with the Geological Survey of Denmark and Greenland.
“It’s dead ice. It will just melt and disappear from the ice sheet,” Colgan said in an interview. “This ice has been sent to the ocean no matter what climate (emissions) scenario we take now.”
Lead author Jason Box, a glaciologist with the Greenland survey, said it’s “more of a foot in the grave.”
The unavoidable 10 inches in the study is more than twice the sea level rise scientists previously expected from the melting of the Greenland ice sheet. The study in the journal Nature Climate Change said it could grow as high as 30 inches (78 centimeters). By contrast, last year’s report from the Intergovernmental Panel on Climate Change predicted a range of 2 to 5 inches (6 to 13 centimeters) for likely sea level rise from the melting of the Greenland ice by the year 2100.
What scientists did for the study was look at the ice in balance. In perfect balance, snowfall in the mountains of Greenland flows down and charges and thickens the sides of glaciers, balancing melting at the edges. But in recent decades, there has been less replenishment and more melting, creating imbalance. 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 if the world reduces carbon pollution, Colgan said.
“I think starving would be a good term,” for what’s happening to the ice, Colgan said.
One of the study’s authors said more than 120 trillion metric tons (110 trillion metric tons) of ice are already doomed to melt due to the warming ice sheet’s inability to replenish its edges. When that ice melts into water, if it were concentrated only over the United States, it would be 37 feet (11 meters) deep.
This is the first time scientists have calculated minimal ice loss — and associated sea level rise — for Greenland, one of Earth’s two massive ice sheets that are slowly shrinking due to climate change from burning coal, oil and natural gas. Scientists used an accepted technique for calculating the minimum recorded ice loss, the technique used on mountain glaciers for the entire giant frozen island.
Pennsylvania State University glaciologist Richard Alleywho was not part of the study, but said it made sense, said the committed melting and sea level rise is like an ice cube put in a cup of hot tea in a warm room.
“You have committed massive loss of the ice,” Alley said in an email. “In the same way, most mountain glaciers and the rims of Greenland would continue to lose mass if temperatures stabilized at modern levels, because they were put in warmer air, just like your ice cube was put in warmer tea.”
While 10 inches doesn’t sound like much, that’s a global average. Some coastal areas will be hit with more, plus floods and storms could be even worse, so that much sea level rise “will have huge social, economic and environmental impacts,” said Ellyn Enderlin, a professor of geosciences at Boise State University.
Time is the key unknown here and a bit of a problem with the study, said two outside ice scientists, Leigh Stearns of the University of Kansas and Sophie Nowicki of the University at Buffalo. The researchers in the study said they couldn’t estimate the timing of the committed melting, but in the last sentence they call it “within this century,” without backing it up, Stearns said.
Colgan replied that the team doesn’t know how long it will take for all the doomed ice to melt, but with an educated guess it would probably be by the end of this century or at least by 2150.
Colgan said this is actually all a best case scenario. The year 2012 (and to a different extent 2019) was a massive melting year, when the balance between adding and subtracting ice was most out of balance. If Earth begins to undergo more years like 2012, Greenland’s melting could lead to 30 inches (78 centimeters) of sea level rise, he said. Those two years now seem extreme, but years that look 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.”