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20 April 2017

NASA Study Links Glacier Shape to Melting Susceptibility

The terminus of the Kangerlugssuup Sermerssua glacier, Western Greenland   - Img: Timothy Bartholomaus, Univ. of Idaho
With global temperatures on the rise due to climate change, the planet’s ice caps and glaciers are fighting an on-going battle for survival, and losing. As such, gaining an understanding of the factors which influence the rate at which they melt is vital in predicting future changes and patterns, formulating a plan to combat such effects, and hopefully slow, halt, or reverse the process altogether, although the latter seems rather unlikely at this point.

On that front, a newly published NASA-funded study seems to have made a breakthrough; by analysing the shape of Greenland’s glaciers, they have managed to identify which among them are most susceptible to thinning, or melting, in the coming decades. They claim that the research “could help predict how much the Greenland Ice Sheet will contribute to future sea level rise in the next century, a number that currently ranges from inches to feet”.

As home to the second largest ice sheet on the planet, the largest of course being Antarctica, Greenland’s fate will have a noticeable and lasting impact on the world at large. The ice sheet has been losing mass for decades, but the change in mass of individual coastal glaciers is highly variable, and as such hard to predict. The study, published in Nature Geoscience on April 17th by lead author Denis Felikson, a graduate research assistant at the University of Texas Institute for Geophysics (UTIG) and a PhD student in the University of Texas Department of Aerospace Engineering and Engineering Mechanics, sought to change this.

“We were looking for a way to explain why this variability exists, and we found a way to do it that has never been applied before on this scale,” Felikson said, “There are glaciers that popped up in our study that flew under the radar until now.”

The study involved the investigation of 16 of Western Greenland’s glaciers, and ultimately identified four among them as the most susceptible to thinning, the glaciers in question being; Rink Isbrae, Umiamako Isbrae, Jakobshavn Isbrae, and Sermeq Silardleq.

Rink Isbrae has so far been stable since 1985, but the same cannot be said of Umiamako Isbrae, Jakobshavn Isbrae, and Sermeq Silardleq. Jakobshavn Isbrae alone is reportedly responsible for more than 81% of West Greenland’s total mass loss over the past three decades, whilst Umiamako Isbrae and Sermeq Silardleq have also begun to lose mass. The shape analysis found that should its terminus become unstable, Rink Isbrae could easily join them.

"Not long ago we didn't even know how much ice Greenland was losing, now we're getting down to the critical details that control its behaviour," said Tom Wagner, director of NASA’s cryosphere program, which sponsored the research.

The susceptibility of a glacier to melting is dependent upon its thickness and surface slope, with thinning spreading more easily across thick and flat glaciers and with more difficulty across thin and steep portions of glaciers, generally speaking of course. The former factors are in turn influenced by the landscape beneath the glacier. In order to ascertain said susceptibility, the analysis focused on calculating just how far inland the thinning each glacier, which begins at the terminus, is likely to extend, as those with thinning that reaches far inland are the most susceptible to ice mass loss. 

They achieved this via use of a bedrock topography map created with data from NASA’s Ocean Melting Greenland project, with which they were able to determine the thickness of the ice, and a digital elevation model from the Greenland Ice Mapping Project, which uses measurements from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA’s Terra satellite to separate glacier catchments. This, alongside other data sources, enabled the team to identify the areas of Greenland most vulnerable to melting.

Study co-author Timothy Bartholomaus, an assistant professor at the University of Idaho, said of the research, “The approach we demonstrate here allows us to identify which outlet glaciers are not yet changing rapidly, but might. With that knowledge, we can anticipate potential sea-level rise and set up the observational campaigns in advance to understand these glacier changes.”

The research revealed that most glaciers are susceptible to thinning between 10 and 30 miles inland; Jakobshavn Isbrae, however, is under more severe a threat. The risk of thinning at Jakobshavn Isbrae reaches over 150 miles inland, which amounts to almost one-third of the way across the Greenland Ice Sheet. If left to continue at this rate, the resulting effects could be substantial, and not at all desirable.

Ginny Catania, an associate professor in the University of Texas Jackson School of Geosciences and research associate at UTIG, said of the group’s future ambitions, “Our plan is to extend the analysis so that we can identify glaciers in Antarctica and around the rest of Greenland that are most likely to be susceptible to change in the future.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.