Greenland’s glaciers are melting faster | ET REALITY


Greenland’s mountain glaciers and floating ice shelves are melting faster than just a few decades ago and becoming destabilized, according to two separate studies published this week.

The island’s peripheral glaciers, located mainly in coastal mountains and not directly connected to the larger Greenland ice sheet, retreated twice as fast between 2000 and 2021 as before the turn of the century, according to a study published Thursday.

“It became much more difficult to be a glacier in Greenland in the 21st century than even in the 1990s,” said Yarrow Axford, professor of geological sciences at Northwestern University and co-author of the paper, published in the journal Nature Climate Change.

Dr. Axford’s team found that glaciers in southern Greenland have shortened by 18 percent on average since 2000, and glaciers in other parts of the island have shortened by 5 to 10 percent.

“These glaciers react very quickly to climate changes,” said Laura Larocca, lead author and NOAA postdoctoral fellow at Northern Arizona University. Since 2000, temperatures in the Arctic have increased twice as fast as the global average temperature.

The researchers compared historical photographs dating back to the 1930s with modern satellite measurements of more than 1,000 glaciers. By converting both types of images into digital maps, the researchers were able to measure the extent to which the glaciers’ endpoints had retreated over the years.

Ice melting into the ocean from Greenland is one of the largest contributors to global sea level rise. Glaciers are also important locally for maintaining natural ecosystems and biodiversity, and for providing electricity through hydropower. Some Greenlanders even rely on glacial meltwater for drinking. As the ice melts, more water will be temporarily available, but if warming is not controlled, the ice and meltwater will eventually run out.

Outlying glaciers can be an “early warning system” for the rest of Greenland’s snow and ice, Dr Axford said. Individual glaciers are small compared to the vast ice sheet that covers the country’s interior, although some could still dwarf entire cities and respond more directly to the warming atmosphere. These glaciers only make up about 4 percent of Greenland’s total ice sheet, but they account for about 14 percent of the island’s ice loss. As a result, they are contributing disproportionately to sea level rise.

That could change as the ice sheet itself becomes less stable. Greenland’s northern coast is buttressed by floating ice shelves that prevent inland glaciers, which are part of the ice sheet, from flowing freely into the Arctic Ocean.

According to an independent study, the volume of these ice shelves has decreased by more than 35 percent since 1978. published Tuesday in Nature Communications. Most of the ice is melting from the bottom, as the ocean beneath the floating platforms warms. Three ice shelves in northern Greenland have already almost completely collapsed, all in the last 20 years. After one of these collapses, ice loss from the glacier behind the shelf more than doubled.

“It’s like removing bricks from an ice dam,” said Romain Millan, a glaciologist at Grenoble Alpes University in France and lead author of the paper.

The research published this week is based on the work of Anders Bjork, assistant professor of geography at the University of Copenhagen and co-author of both papers. He has been traveling to Greenland since 2006 and said evidence of shrinking glaciers was clearly visible across the landscape.

“The glaciers are receding, but they are also thinning,” he said. “It’s not just that you have to walk longer to get to the ice, but suddenly mountains appear.” As the ice retreats from the Greenland coast, new islands are also appearing in the fjords.

Despite these anecdotal signs, only recently have scientists been able to measure how quickly the ice is disappearing, thanks to more complete bird’s-eye views provided by satellites and recently discovered archival photographs. About 15 years ago, Dr. Bork and his colleagues found a reserve of approximately 200,000 historical photographs taken by Danish pilots during the mapping expeditions of the early 20th century in Greenland.

“People had forgotten they existed,” he said. The images provide invaluable data from decades before satellite observations began, allowing researchers to trace changes in the ice sheet back in time. Other glaciologists have recently conducted similar studies using historical photographs from Svalbard and Switzerland.

The consistent trend in so many glaciers studied in this new research shows strong evidence that global climate change is causing their disappearance, as opposed to more local, short-term natural variability, said Ginny Catania, professor of earth and planetary sciences at the University of Texas at Austin, which was not involved in either study.

“There is no other way to explain the coincidental retreat of hundreds of glaciers,” he said. “When everyone does that, it’s remarkable.”

Understanding these past changes can help climate scientists better predict the future.

This week’s two new papers show great promise for improving people’s understanding of future sea level rise, said Twila Moon, associate principal scientist at the National Snow and Ice Data Center at the University of Colorado Boulder, who did not participate in any of the studies. Researchers would still need to take some intermediate steps to incorporate these findings into climate models and sea-level rise budgets, Dr. Moon said, so she expects the process to take time.

The latest report from the Intergovernmental Panel on Climate Change projects that, by 2050, global average sea level will likely rise between 7 and 9 inches, or 18 to 23 centimeters. By 2100, they are likely to rise by more than a foot or even more than two feet. The behavior of ice shelves is one of the greatest uncertainties that currently complicates these estimates.

These two studies together highlight that even the world’s northernmost glaciers are melting rapidly and that the ice shelves right next to them are vulnerable to collapse, Dr. Bjork said. “It is now very clear that glaciers, both large and small, from the smallest to the ice sheet, have entered a new phase.”

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