A study published on Monday showed that rapid melting of the Greenland ice sheet will eventually raise global sea levels by at least 10.6 inches (27 cm) – more than double what was previously expected.
This is because of something that could be called zombie ice. This is doomed ice that, while still attached to thicker areas of ice, is no longer replenished by parent glaciers now receiving less snow. Without replenishment, ice exhausted by climate change will melt and will inevitably lead to sea level rise, said study co-author William Colgan, a glaciologist with the Geological Survey of Denmark and Greenland.
“It’s dead ice,” Colgan said in an interview. “It’s going to melt and disappear from the ice sheet.” “This ice has been sent to the ocean, no matter what climate (emissions) scenario we take now.”
It’s “more like one foot in a grave,” said study lead author Jason Books, a glaciologist at the Greenland Survey.
The inevitable 10-inch rise in the study is more than double the sea-level rise as scientists had previously predicted from melting Greenland’s ice sheet. The study, published in the journal Nature Climate Change, said it could be as high as 30 inches (78 cm). By contrast, last year’s IPCC report projected a range of 2 to 5 inches (6 to 13 cm) of potential sea-level rise from melting Greenland’s ice by 2100.
What the scientists did for the study was to look at the ice in equilibrium. In perfect balance, snowfall in the mountains of Greenland flows downward and recharges and thickens the sides of glaciers, balancing what melts at the edges. But in the past few decades, there has been less renewal and greater melting, which has led to an imbalance. The study authors looked at the proportion of what is being added to what is lost and calculated that 3.3% of Greenland’s total ice volume will melt regardless of what happens as the world reduces carbon pollution, Colgan said.
“I think hunger would be a good phrase” for what happens to the ice, Colgan said.
One of the study’s authors said that more than 120 trillion tons (110 trillion metric tons) of ice is already doomed to melt from the inability of the warm ice sheet to regenerate its edges. When this ice melts in water, if it were concentrated just over the United States, it would be 37 feet (11 meters) deep.
The numbers are a global average of sea level rise, but some places farther from Greenland will increase and less places close, such as the east coast of the United States. Although 10.6 inches may not seem like much, this would be above tides and storms, making them worse, so this significant sea level rise “would have huge social, economic and environmental impacts,” said Ellen Enderlin, professor of Earth sciences. at Boise State University, who was not part of the study.
“This is a really big loss and it will have a detrimental impact on coasts around the world,” said New York University’s David Holland, who has just returned from Greenland but is not part of the study.
This is the first time scientists have calculated minimal ice loss – and attendant sea level rise – in Greenland, one of Earth’s two massive ice sheets that are slowly shrinking due to climate change from burning coal, oil and natural gas. The scientists used an accepted technique to calculate minimal ice loss, the method used in the mountain glaciers of the entire giant frozen island.
The melting and rising sea levels are like an ice cube placed in a cup of hot tea in a warm room, said Richard Alley, a Pennsylvania State University glaciologist who was not part of the study but said it makes sense.
“You made a collective loss of ice,” Ally said in an email. “In the same way, most of the world’s mountain glaciers and fringes of Greenland would continue to lose mass if temperatures stabilized at modern levels because they were placed in warmer air like an ice cube was placed in a warm tea.”
Two outside glaciologists, Lee Stearns of the University of Kansas and Sophie Nowicki of the University at Buffalo, said time is the unknown key here and there is a small problem with the study. The study researchers said they couldn’t estimate the timing of committed melting, but in the last sentence they mentioned, “during this century” without backing it up, Stearns said.
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Colgan replied that the team doesn’t know how long it will take for all of the stricken ice to melt, but an informed guess, likely by the end of this century, or at least by 2150.
That’s actually the best-case scenario, Colgan said. 2012 (and to a different degree 2019) was a year of huge melt, when the balance between adding and subtracting ice was lopsided. And if the Earth begins to undergo more years like 2012, he said, Greenland’s melt could lead to a rise of 30 inches (78 centimeters) in sea level. He said those two years seem extreme now, but years that seem normal now would have been extreme 50 years ago.
“This is how climate change works,” Colgan said. “Today’s outliers become tomorrow’s averages.”
Copyright © 2022 by The Associated Press. All rights reserved.
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