NASA finds out what glacier slope is showing around Greenland ice sheet thinning


IMAGE: GIF showing the distances at which thinning may spread into the interior of Greenland. Glaciers in higher elevation areas tend to be less inland than those in lower visibility areas … more

Credit: Credits: Denis Felikson

As glaciers erupt from Greenland’s ice sheet, their subsoils suggest their role in future ice thinning and sea level rise.

The glaciers outside the ice rivers flow within the bedrock fissures and drain into the surrounding sea. They retreat and begin to shrink as the climate warms, and this thinning works toward the center of the ice sheet. Now, by looking at the shape of the bed under the ice, scientists have a better understanding of which glaciers could have a significant effect on what the Greenland Ice Sheet does. contribute to rising sea levels in future years. They found that some glaciers flowing over calmer slopes could have a greater impact than previously thought. The gentle slopes allow thinning to spread from the edge of the ice sheet far into the interior, but glaciers with steep falls in the terrain of their beds limit the length of time. -into the internal thinning that can spread.

The research, published on December 11 in Geophysical Research Letters, we surveyed 141 outer glaciers on the Greenland ice sheet to predict how far into the inner attenuation that could spread on their stream lines, start from the edge of the ocean.

“What we’ve found is that some glaciers flow over these steep waterfalls in bed, and some don’t,” said lead author Denis Felikson with NASA’s Goddard Space Flight Center the Greenbelt, Maryland, and the Universities Space Research Association (USRA). “For the glaciers that have that steep fall in bed, thinning can’t get past those drops.” Borrowing a term from geomorphology – the study of the Earth’s physical features – they kept these steep features “knickpoints.”

When a river flows over a hillside, it often leads to a waterfall or lake. But for glaciers, cas is a relative term that actually translates to just three levels of slope. “It’s not like the ice is going over a cliff,” Felikson said. “But in terms of glacier dynamics, they’re very steep – an order of magnitude steeper than a normal bed to which the ice flows.”

The researchers were able to identify these “steep” changes in topography using digital elevation models of the ice sheet bed and surface topography. Surface terrain came from the Greenland Ice Mapping Project, created using NASA’s Advanced Spaceborne Thermal Temperature Radiometer (ASTER) instrument that flies aboard NASA’s Terra satellite, in conjunction with data from NASA, Ice, Cloud, and Elevation Satellite (ICESat) missions. The bed-top digital elevation model, called the BedMachine dataset, is a high-resolution model of the bed under the Greenland ice sheet, created using data from NASA’s Operation IceBridge air studies on polar ice.

“This bed topography dataset was critical for us to do our job,” Felikson said. “And it’s thanks to NASA’s remote sensing, which is Operation IceBridge’s studies, that we’ve been able to do this.” Using the remote sensing data, scientists were able to compare topographic measures to make a single metric according to a glacier’s flow line. This helped them to identify a resting place between the ice parts up and down the glacial ice.

Ice below the hilly area tends to thin out from the edge of the glacier. But the thinning does not extend beyond this point upstream, so the interior of the ice sheet is unaffected.

Of all the glaciers seen, a majority (65 percent) had recognizable peak points. Hill points are particularly common in the more mountainous areas of Greenland, where several of the largest and fastest moving glaciers show relatively close hill points. the east. Given their vertical size, these glaciers could contribute significantly to thinning and melting of ice, but with their hilly locations close to the coast, thinning is not expected to spread far. into the country.

However, glaciers are found to have gradual glaciers that flow through a gentle, or no-knock, landscape. These glaciers are of interest, and concern, because even those that are smaller in size have the potential to allow thinning to extend hundreds of kilometers inland, eroding the heart of the plateau. ice.

“They can be influential in raising sea levels, not because they are large and deep, but because they have access to more ice that they can eat away,” Felikson said. longer to respond, but over the long term they could potentially contribute as much to sea level rise as possible to the larger glaciers. ”

Over the calm landscape of the north-west coast of Greenland, nine dozen adjacent glaciers are expected to narrow more than 250 km (155.3 miles) into the interior of the ice sheet, over an area? 140-km (86.9 miles) wide. The Northwest region of the ice sheet is the only area that has seen a steady increase in ice distribution over recent decades, and Felikson predicts that they will continue to do so with the features of these glaciers.


This work was initiated at the University of Texas as part of Felikson’s dissertation and continued throughout his time at NASA Goddard. The origins of the hills and their long-term effects of thinning, as well as Greenland’s contribution to sea level rise, remain the basis for future research.

The data used in this study can be found at:
https: // /table /4284759

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