Ice on the Greenland Ice Sheet not only melts. The ice actually slips quickly across his bed to the edges of the ice cover. As a result, ice is moved faster than previously thought to the refractory fringes because ice movement is caused not by ice deformation but by gliding.
Neil Humphrey, Professor of Geology and Geophysics at the University of Wyoming, and Nathan Maier, Ph.D. The student from Morristown, New Jersey, recently led a research group that discovered that you do not need beds with a bottom or sludge that acts as a lubricant to achieve high slip rates. Rather, they found that it is over hard rock, where the ice slips off faster. In addition, the ice slides much more about the rock than predicted in previous theories.
"That's the kicker." The Greenland ice glides happily over a surface that theoretically should not be able to slip fast, "says Humphrey. "What's important is that you put a lot of ice in the oceans or at low altitudes where it can melt very quickly, it's like a lump of molasses slipping off the continent, it just does not melt, it slips in Direction." the ocean. "
" Our measurements of the slip-dominated flow over a hard bed in a slow-moving region were quite surprising, as these regions are not normally associated with heavy gliding, "adds Maier." In general, people associate many gliding movements with regions that have soft soils (mud) or exceptionally high sliding speeds, such as. B. ice streams. However, in this relatively boring region we have found the highest amount of sliding that has been measured so far. "
Maier was lead author and Humphrey co-author of the paper entitled" Sliding Dominates Slow-Flowing Margin Regions, Greenland Ice Sheet "  The Science Review (19459015) published in Science Advances The peer-reviewed, multidisciplinary open access science journal covers all areas of science, including life sciences, physics, social sciences, computer science, and environmental science. [19659005OthercontributorsincludeJoelHarperAssociateProfessorofEarthSciencesandTobyMeierbachtolAssistantProfessorattheUniversityofMontanaThepaperpresentsworksthatwereconductedontheGreenlandIceSheetfrom2014to2016
Researchers installed 212 Inclination sensors in a network of boreholes, which can be found in the Eisb were drilled. The tilt sensors allow the observation of ice deformation and sliding movement. Humphrey uses a large-bore drill he designed, which he calls "a very large truck washing machine" that ejects high-pressure steam with a large bore nozzle and hydraulic hose. He says it's "the world's fastest ice drilling machine" and can drill 5,000 feet into the Greenland ice sheet in eight hours.
"Most of our work is truly mysterious," says Humphrey. "We drill holes in the ice, but do not even collect ice cores."
The modeling, which is constrained by detailed inclination observations along the base ice surface, suggests that the high slip is due to a slippery ground, where sparsely spaced bedrock surveys provide limited sliding resistance. Slip velocity estimates are usually based on the residual between the observed surface velocity and the modeled ice deformation rate.
"We do not have a good theory for this type of gliding," explains Humphrey. "But the data in this article will allow us to work on an improved theory."
Maier agrees that her work should help to improve the accuracy of ice sheet models when attempting to predict the future mass loss from Greenland.
"There was some debate as to whether the ice flow along the edges of Greenland should be viewed as largely deformed or largely skidding," says Maier. "This has to do with the uncertainty of calculating the deformation motion with surface measurements only, our direct measurements of the sliding-dominated motion and the sliding measurements of other Greenlandic research teams are a pretty convincing argument no matter where you go on the edges of Greenland."
According to Maier, this is important for the future of Greenland, as the ice sheet can move the mass efficiently and thus react quickly to changes Climate.
Similarly, Maier says that changes in ice movement due to a warming climate will also cause thickening and thinning at the edges of the ice sheet. Since ice can be moved efficiently due to high sliding speeds, rapid changes in melting can occur.
Gliding ice has two functions, according to Humphrey. First, the ice can slip into the ocean and form icebergs, which then float away. Second, the ice slides into a lower, warmer climate where it can melt faster.
While it sounds horrible, Humphrey notes that the entire Greenland ice sheet is 5,000 to 10,000 feet thick.
"In a really great year of melting, the ice could melt a few meters, which means Greenland will be there for another 10,000 years," says Humphrey. "So it's not the disaster that floods the media."
Humphrey has been working in Greenland for 30 years and says that the Greenland ice sheet melted only 3 meters during this time.
Clouds dominate the uncertainties in predicting the future melt of Greenland
"Slides dominate slow-flowing marginal regions, Greenland Ice Sheet" Science Advances (2019). DOI: 10.1126 / sciadv.aaw5406, https://advances.sciencemag.org/content/5/7/eaaw5406
Researchers discover that ice from the Greenland ice sheet slips towards the edges (2019, July 10)
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