Greenland’s Biggest Losers
Recently’s story was adapted from an article published by NASA, The National Aeronautics and Space Administration’s Jet Propulsion Laboratory.
The Greenland Ice Sheet has shed about one-fifth more ice mass in the past four decades than previously estimated, researchers at NASA, The National Aeronautics and Space Administration’s Jet Propulsion Laboratory in Southern California reported in a new paper. The majority of glaciers on the landmass have retreated significantly, and icebergs are falling into the ocean at an accelerating rate. This additional ice loss has had only an indirect impact on sea levels, but it can hold implications for ocean circulation in the future.
Published in Nature on January 17, 2024, the analysis offers a comprehensive look at retreat around the edges of the entire ice sheet from 1985 to 2022, drawing from nearly a quarter million pieces of satellite data on glacier positions. Of the 207 glaciers in the study, 179 retreated significantly since 1985. Twenty-seven held steady, and one advanced slightly.
Most of the ice loss came from below sea level, in fjords on Greenland’s periphery. Once occupied by ancient glacial ice, several of these deep coastal valleys have filled with seawater—meaning the ice that broke off made little net contribution to sea level. But the loss likely accelerated the movement of ice flowing down from higher elevations, which in turn added to sea level rise.
“When the ice at the end of a glacier calves and retreats, it’s like pulling the plug out of the fjord, which lets ice drain into the ocean faster,” said Chad Greene, a glacier scientist at JPL and the study’s lead author.
Icebergs have tumbled from Greenland’s glaciers for thousands of years as part of a natural cycle that typically balanced glacier growth in the winter with melting and retreat in the summer. The new study finds that ice retreat has far outpaced growth throughout the 21st century. The researchers also found that Greenland’s ice extent remained relatively steady from 1985 to 2000, then started a marked recession that continues to this day.
The data showed a glacier in northeast Greenland called Zachariæ Isstrøm (above) lost the most ice, dropping 176 billion tons (160 billion metric tons) of mass due to retreat. It was followed by Sermeq Kujalleq (Jakobshavn Glacier) on the western coast (top of this page), which lost an estimated 97 billion tons (88 billion metric tons), and Humboldt Gletscher in the northwest, which lost 96 billion tons (87 billion metric tons).
Only one glacier, Qajuuttap Sermia in southern Greenland, experienced any growth over the study period, but its gains were too small to offset the losses from other glaciers.
The researchers also found that glaciers with the largest seasonal fluctuations in the position of their ice front experienced the greatest overall retreat. The correlation suggests the glaciers that are most sensitive to warming each summer will be most impacted by climate change in the coming decades.
The discovery of a large-scale pattern of glacier retreat and its link to glacier sensitivity on seasonal time scales was the result of a big-data synthesis that looks at all parts of the ice sheet over time, said Alex Gardner, a cryospheric scientist at JPL and co-author of the paper. Scientists drew from five publicly available datasets that cumulatively tracked the month-to-month positions of 236,328 glacier edges as detected, either manually or by computer algorithms, in images collected by optical and radar satellites.
“Previously, we had bits and pieces—lots of local studies,” Gardner said. “But what this study offers is a systematic and comprehensive view that has led to some pretty significant insights that we didn’t have about the ice sheet before.”
NASA, The National Aeronautics and Space Administration Earth Observatory animations by Lauren Dauphin, using Landsat data from the United States. Geological Survey and glacier position information provided by Greene, C.A., et al. Story by Andrew Wang (NASA, The National Aeronautics and Space Administration JPL).
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