AUSTIN, Texas – More of the world’s coastal glaciers are melting faster than ever, but exactly what caused the large-scale retreat has been difficult to pinpoint due to natural fluctuations in the glaciers’ environment. Now, researchers from the University of Texas Institute for Geophysics (UTIG) and Georgia Tech have developed a methodology that they believe is cracking the code of why coastal glaciers are retreating, and in turn, how much can be attributed to human-induced climate change. Attributing the human role to coastal glaciers – which melt directly into the sea – could pave the way for better predictions of sea level rise.
So far, scientists have only tested the approach in computer models using simplified glaciers. They found that even modest global warming caused most glaciers to melt or retreat.
The next step, the researchers said, is for scientists to simulate the coastal glaciers of a real ice sheet, such as that of Greenland, which contains enough ice to raise sea levels by about 7 meters. That will show whether they are retreating due to climate change and help predict when the next major ice loss may occur.
“The methodology we propose is a roadmap to making confident statements about what the human role is [in glacial retreats]said glaciologist John Christian, a postdoctoral researcher at both the University of Texas at Austin and Georgia Tech. “Those statements can then be communicated to the public and policymakers and aid in their decision-making.”
Published on July 13 in the news The cryosphere, the methodology is unique in that it treats rapid glacier retreat as an individual probability event, such as a wildfire or tropical storm. For a major retreat to occur, the glacier must retreat past its “stability threshold,” which is usually a steep rise in the underlying rock that helps slow the flow. The likelihood of that happening depends on the local climate and ocean conditions that change with natural fluctuations and human-induced warming. Even small variations can cause major changes in a glacier’s behavior, making them difficult to predict and leading to cases where glaciers retreated right next to glaciers that were not.
That, said co-author and UTIG glaciologist Ginny Catania, is why the latest report from the Intergovernmental Panel on Climate Change found there was still too much uncertainty about coastal glaciers to say whether their retreat is due to human activity. caused climate change or natural climatic variations.
The new study shows how uncertainty can be overcome by providing a methodology that takes into account differences between glaciers and natural climate variability, while testing the effect of background trends such as global warming. According to Catania, the study means they can now attribute mass glacier retreat along the coast to climate change, not just natural variability.
“And that’s the first time anyone’s done that,” she said.
To test the methodology, the team ran thousands of simulations over the past 150 years with and without global warming. The simulations showed that even modest warming dramatically increases the likelihood of glacier retreat across the entire ice sheet.
When the scientists used models without human-induced climate change, they found that it was virtually impossible for more than a few glaciers to start retreating within years of each other.
By contrast, since 2000, nearly all (200) of Greenland’s 225 coastal areas glaciers have been in various states of retreat.
“This study gives us a toolbox to determine the role of humans in the loss of ice from Greenland and Antarctica, to say with confidence that it’s not just coincidence,” said Georgia Tech glaciologist and co-author Alex Robel.
The research on coastal glaciers builds on previous work to understand the human role in mountain glacier retreat — which is now well established. The latest study was funded by UTIG and the National Science Foundation. UTIG is a research division of UT Austin’s Jackson School of Geosciences
Overlapping simulations of a glacier, one with climate change and the other without. Glaciers melt dramatically as they retreat past their stabilizing threshold, shown here as a peak in the bedrock. According to research from the University of Texas Institute for Geophysics and Georgia Tech, that becomes much more likely with climate change. Animation: John Erich Christian/University of Texas Institute for Geophysics/Georgia Tech
Thanks to UT News.
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