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‘Zombie ice’ will raise sea level by 10 inches, a new study says

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Greenland’s rapidly melting ice sheet will eventually raise global sea level by at least 10.6 inches — more than twice as much as previously forecast — according to a study published Monday.

That’s because of something that could be called “zombie ice.” That’s doomed ice that, while still attached to thicker areas of ice, is no longer getting replenished by parent glaciers now receiving less snow. Without replenishment, the doomed ice is melting from climate change and will raise seas, said study co-author William Colgan, a glaciologist at the Geological Survey of Denmark and Greenland.

“It’s dead ice. It’s just going to melt and disappear from the ice sheet,” Colgan said in an interview. The melting will happen regardless of efforts worldwide to reduce carbon emissions, he said.

The unavoidable 10 inches in the study is more than twice as much sea level rise as scientists had expected from the melting of Greenland’s ice sheet. The study in the journal Nature Climate Change said it could reach as much as 30 inches. By contrast, last year’s Intergovernmental Panel on Climate Change report projected a range of 2 to 5 inches for likely sea level rise from Greenland ice melt by the year 2100.

What scientists did for the study was look at the ice in balance. Ideally, snowfall in the mountains in Greenland flows down and recharges and thickens the sides of glaciers, balancing out what’s melting on the edges. But in the past few decades, there’s less replenishment and more melting, creating imbalance.

“I think starving would be a good phrase” for what’s happening to the ice, Colgan said.

One of the study authors said that more than 120 trillion tons of ice is already doomed to melt from 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 deep.

Although 10.6 inches may not sound like much, this would be over and above high tides and storms, making them even worse, so this much sea level rise “will have huge societal, economic and environmental impacts,” said Ellyn Enderlin, a geosciences professor at Boise State University in Idaho who wasn’t part of the study.

Colgan said the team doesn’t know how long it will take for all the doomed ice to melt, but making an educated guess, it would probably be by the end of this century or at least by 2150.

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