Hombie ice from the massive Greenland ice sheet will eventually raise global sea levels by at least 10 inches (27 centimeters) by itself, according to a study published Monday.
Zombie or doomed ice is ice that is still attached to thicker sections of ice, but is no longer fed by these larger glaciers. This is because the main glaciers receive less filling snow. Meanwhile, the doomed ice is melting from climate change, said study co-author William Colgan, a glaciologist at the Geological Survey of Denmark and Greenland.
“This is dead ice. It’s just going to melt and disappear from the ice sheet,” Colgan said in an interview. “This ice was sent to the oceanregardless of what climate (emissions) scenario we accept now.”
Lead study author Jason Box, a glaciologist with the Greenland Survey, said it was “more like one foot in the grave”.
The imminent ten 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 Nature Climate Change said to be up to 30 inches (78 centimeters). In contrast, last year’s Intergovernmental Panel on Climate Change report predicts a range of 2 to 5 inches (6 to 13 centimeters) of likely sea level rise from melting Greenland ice by 2100.
What the scientists did for the study was to look at the ice in balance. In perfect balance, snowfall in the mountains in Greenland flows down and recharges and thickens the glacier walls, balancing what melts at the edges. But in the last few decades there has been less replenishment and more melting, creating an imbalance. The study’s authors looked at the ratio of what is being added to what is being lost, and calculated that 3.3% of Greenland’s total ice volume would melt regardless of what happens to the world’s reduction in carbon pollution , Colgan said.
“I think starvation would be a good phrase” for what’s happening to the ice, Colgan said.
One of the study’s authors said more than 120 trillion tons (110 trillion metric tons) of ice is already doomed to melt from the warming ice sheet’s inability to replenish its edges. When that ice melted into water, if it was concentrated just over the United States, it would be 37 feet (11 meters) deep.
This is the first time scientists have calculated minimal ice loss – and accompanying sea level rise – for Greenland, one of Earth’s two massive ice sheets which slowly shrink due to climate change from the burning of coal, oil and natural gas. The scientists used an accepted technique to calculate the minimum ice loss, the one used on mountain glaciers for the entire giant frozen island.
Pennsylvania State University glaciologist Richard Alley, who was not involved in the study but said it makes sense, said the melting and sea-level rise that has occurred is like an ice cube placed in a cup of hot tea in a warm room.
“You took a massive loss off the ice,” Alley said in an email. “Similarly, most of the world’s mountain glaciers and the edges of Greenland will continue to lose mass if temperatures stabilize at modern levels because they were placed in warmer air, just as your ice cube was placed in warmer tea.’
While 10 inches doesn’t sound like much, it’s a global average. Some coastal areas will be affected more, and the tides and storm surges on top of that could be even worse, so this big rise in sea level “will have huge social, economic and impact on the environment” said Elin Enderlin, professor of geosciences at Boise State University.
Weather is the key unknown here and a bit of a problem with the study, said two outside ice scientists, Lee Stearns of the University of Kansas and Sophie Nowitzki of the University at Buffalo. The researchers in the study said they could not estimate when the melting occurred, but in the last sentence they mentioned “within this century” without backing it up, Stearns said.
Colgan replied that the team did not know how long it would take for all of the doomed ice to melt, but made an educated guess that it would probably be by the end of this century, or at least by 2150.
Colgan said that’s actually the best case scenario. The year 2012 (and to varying degrees 2019) was a huge melting year, when the balance between adding and subtracting ice was most out of balance. If Earth starts experiencing more years like 2012, Greenland’s melting could cause 30 inches (78 centimeters) of sea level rise, he said. Those two years look extreme now, but years that look normal now would have been extreme 50 years ago, he said.
“This is how climate change works,” Colgan said. “Today’s outliers become tomorrow’s averages.”
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