Scientific team uncovers additional threat to Antarctica’s floating ice shelves

UCI, NASA JPL scientists uncover additional threat to Antarctica’s floating ice shelves
Ice melange, a mix of ice shelf fragments, windblown snow and frozen seawater, can act as a glue to fuse massive rifts in floating ice in Antarctica. Researchers at UCI and NASA JPL discovered {that a} thinning of the substance over time could cause rifts to open, resulting in the calving of enormous icebergs. Credit score: Beck / NASA Operation IceBridge

Glaciologists on the College of California, Irvine and NASA’s Jet Propulsion Laboratory have examined the dynamics underlying the calving of the Delaware-sized iceberg A68 from Antarctica’s Larsen C ice shelf in July 2017, discovering the seemingly trigger to be a thinning of ice melange, a slushy concoction of windblown snow, iceberg particles and frozen seawater that usually works to heal rifts.

In a paper revealed right this moment in Proceedings of the Nationwide Academy of Sciences, the researchers report that their modeling research confirmed melange thinning to be a significant driver of ice shelf collapse. The circulation of ocean water beneath ice shelves and radiative warming from above, they are saying, regularly deteriorate ice melange over the course of a long time.

As ice cabinets are thought to buttress and forestall land-borne glaciers from extra quickly flowing into the ocean, this new data about rift dynamics illuminates a beforehand underappreciated hyperlink between local weather change and ice shelf stability.

“The thinning of the ice melange that glues collectively massive segments of floating ice cabinets is one other means local weather change could cause speedy retreat of Antarctica’s ice cabinets,” mentioned co-author Eric Rignot, UCI professor of Earth system science. “With this in thoughts, we could have to rethink our estimates concerning the timing and extent of sea degree rise from polar ice loss—i.e., it may come sooner and with an even bigger bang than anticipated.”

Utilizing NASA’s Ice-sheet and Sea-level System Mannequin, observations from the company’s Operation IceBridge mission, and information from NASA and European satellites, the researchers assessed a whole lot of rifts within the Larsen C ice shelf to find out which of them had been most susceptible to breaking. They chose 11 top-to-bottom cracks for in-depth research, modeling to see which of three situations rendered them most definitely to interrupt: If the ice shelf thinned due to melting, if the ice melange grew thinner, or if each the ice shelf and the melange thinned.

“Lots of people thought intuitively, “If you happen to skinny the ice shelf, you are going to make it far more fragile, and it will break,'” mentioned lead creator Eric Larour, NASA JPL analysis scientist and group supervisor.

As an alternative, the mannequin confirmed {that a} thinning ice shelf with none modifications to the melange labored to heal the rifts, with common annual widening charges dropping from 79 to 22 meters (259 to 72 ft). Thinning each the ice shelf and the melange additionally slowed rift widening however to a lesser extent. However when modeling solely melange thinning, the scientists discovered a widening of rifts from a median annual charge of 76 to 112 meters (249 to 367 ft).

The distinction, Larour defined, displays the totally different natures of the substances.

“The melange is thinner than ice to start with,” he mentioned. “When the melange is barely 10 or 15 meters thick, it is akin to water, and the ice shelf rifts are launched and begin to crack.”

Even in winter, hotter ocean water can attain the melange from beneath as a result of rifts prolong via all the depth of an ice shelf.

“The prevailing idea behind the rise in massive iceberg calving occasions within the Antarctic Peninsula has been hydrofracturing, wherein soften swimming pools on the floor enable water to seep down via cracks within the ice shelf, which develop when the water freezes once more,” mentioned Rignot, who can be a NASA JPL senior analysis scientist. “However that idea fails to elucidate how iceberg A68 may break from the Larsen C ice shelf within the lifeless of the Antarctic winter when no soften swimming pools had been current.”

He mentioned that he and others within the cryosphere research group have witnessed ice shelf collapse on the Antarctic Peninsula, stemming from a retreat that started a long time in the past.

“We’ve got lastly begun to hunt an evidence as to why these ice cabinets began retreating and coming into these configurations that grew to become unstable a long time earlier than hydrofracturing may act on them,” Rignot mentioned. “Whereas the thinning ice melange isn’t the one course of that would clarify it, it is enough to account for the deterioration that we have noticed.”

Becoming a member of Rignot and Larour on this NASA-funded mission had been Bernd Scheuchl, UCI affiliate mission scientist in Earth system science, and Mattia Poinelli, a Ph.D. candidate in geoscience and distant sensing at Delft College of Know-how within the Netherlands.

Slushy iceberg aggregates control calving timing on Greenland’s Jakobshavn Isbræ

Extra info:
Bodily processes controlling the rifting of Larsen C Ice Shelf, Antarctica, previous to the calving of iceberg A68, Proceedings of the Nationwide Academy of Sciences (2021). DOI: 10.1073/pnas.2105080118 ,

Scientific workforce uncovers further menace to Antarctica’s floating ice cabinets (2021, September 27)
retrieved 27 September 2021

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