Scientists Find “Knickpoints” in Greenland That Can Stop Spread of Glacial Thinning

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Greenland Ice Loss Animation

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The rugged surface of Greenland’s mountains is safeguarding a few of the island’s outlet glaciers from warm seaside waters, according to a group of scientists that consisted of researchers from The University of Texas at Austin and NASA.

Outlet glaciers extend from the ice sheet into the sea, where rising ocean heat can accelerate the loss of ice, making the glaciers thinner and raising water level. The researchers discovered that high slopes in the bedrock under the ice type supporting locations the scientists described “knickpoints” that avoid seaside thinning from reaching more inland.

The findings were released on December 11, 2020, in the journal Geophysical Research Letters.

“Thinning in glaciers originates at the edge of the ice, and makes its way inland,” stated lead author Denis Felikson, a NASA research study researcher. “When the thinning reaches a knickpoint that is steep enough, it’s halted.”

However, in areas where the flat bedrock provides no such defense and knickpoints are missing, runaway thinning can reach far into the ice sheet and gnaw at formerly untouched ice and add to water level increase.

Kangilliup Sermia, a Greenland Outlet Glacier

A scientist (Leigh Stearns, The University of Kansas) changes a time lapse cam keeping track of the front of Kangilliup Sermia (likewise called Rink Isbrae), an outlet glacier in Greenland. A brand-new research study including the University of Texas Institute for Geophysics discovered that seaside thinning was stopped for glaciers streaming over high surface, however swept far inland for those like Rink Isbrae which sneak over flatter bedrock. Credit: Tim Bartholomaus

Coauthor Ginny Catania, a teacher of glaciology at the UT Jackson School of Geosciences, stated that a lot of glaciers are thinning as researchers anticipate in a warming environment, however not at the exact same rates or quantities. The irregularity makes it harder to forecast how rapidly water level will increase as the world gets hotter.

“Some glaciers are thinning right next to others that are thickening,” she stated. “Until now we didn’t know how to explain such variability. Denis’ research has provided a framework for that understanding, and it’s very likely that all of the variability we observe in outlet glaciers is linked to variability in the bed topography between glaciers.”

Denis Felikson

The research study’s lead author Denis Felikson, now a research study researcher at USRA and NASA, on a field see to Root Glacier in Alaska when he was a doctoral trainee at UT’s Jackson School. Credit: Denis Felikson

The scientists utilize the term knickpoints to explain high slopes in the bedrock since of their resemblances to river knickpoints–locations that typically form waterfalls or rapids. Like a waterfall, glaciers put over the knickpoints, developing a physical barrier that avoids modifications taking place downstream near the coast from reaching more upstream.

Greenland’s ice sheet covers a location two times the size of Texas. The barrier result of knickpoints is essential since warmer ocean currents are among the primary factors Greenland’s glaciers are losing mass quicker than they were 20 years earlier.

The research study offers researchers a much better understanding of how the loss of ice will play out as the world gets hotter and can likewise focus clinical resources on finding out more about the glaciers more than likely to add to water level increase.

Greenland Ice Loss Animation

An animation proving paths through which ice is lost in Greenland. Analysis of the bed topography discovered that glaciers in Greenland’s northwest area can drain pipes more ice from deep in the interior, while those in more mountainous areas are secured from the worst results of seaside heating. Credit: Denis Felikson

Felikson started the research study while making a Ph.D. at the Jackson School dealing with Catania and coauthor Tim Bartholomaus (now at the University of Idaho) at the University of Texas Institute for Geophysics (UTIG). By comparing the start-stop movement of glacial creep to busy traffic, the UTIG group had actually revealed that a glacier’s shape manages the spread of thinning in a 2017 Nature Geoscience paper.

The present paper constructs on that research study however extends the analysis from 16 to 141 (the bulk) of Greenland’s outlet glaciers, and in doing so, exposed the armoring result of glacial knickpoints.

The research study reveals that glacial knickpoints are remarkably common. Although that may be great news, the research study likewise exposed vulnerability in northwest Greenland, an ignored area of the ice sheet.

“The glaciers in this region could be important over the next 100 years because the relatively flat bedrock beneath them means they can transfer thinning much further into the interior of the ice sheet than some of the larger glaciers in mountainous topography,” Felikson stated.

Catania stated this indicates that water level will increase regardless.

“You’re still going to drain the ice sheet you’re just going to do so through a different area than we thought,” she stated.

The research study group concurred that examinations of the bedrock near the coast is urgently needed to discover how efficient knickpoints are at keeping back seaside warming, as is examination of vulnerable glaciers. Catania and Felikson have actually currently proposed an early caution system that will utilize device discovering to expect instability in glaciers recognized by the knickpoint analysis.

Reference: 11 December 2020, Geophysical Research Letters.
DOI: 10.1029/2020GL090112

Felikson is a research study researcher at Universities Space Research Association and the NASA Goddard Space Flight Center. UTIG is a unit of the Jackson School. The research study was moneyed by a NASA grant and the Gale White Fellowship at UTIG.



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