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Transforming the Antarctic Melting Lake is Dangerous for Ice Shelves and Sea Levels
The dangers of ancient Antarctic ice foreshadow the future of fast-rising seas, but new research may alleviate a nagging fear: that melt ponds destroying ice beneath them can cause prolonged chain reactions that unexpectedly disrupt floating ice shelves. Although the combined melting water destroys ice, the ensuing chain reactions seem short.
However, massive increases in surface melting due to unusually warm weather can cause catastrophic collapse of an ice shelf, such as that of the iconic Larsen B shelf that collapsed in 2002. Now, a study led by a researcher at the Georgia Institute of Technology has modeled chain-breaking reactions and how much water would be needed to replicate this rare, epic collapse.
The disintegration of Larsen B. was preceded by an atypical heat wave that pierced it with molten reservoirs, focusing the researchers' attention on the destruction of the reservoir, also called hydrostructure. They found that the hydrostructuring of a pond can prompt neighboring lakes to do the same.
Too much melted water
"Chain reactions will not spread that far across the ice shelf," says Alex Robel, an assistant professor at Georgia Tech's School of Earth and Atmospheric Sciences. "It will usually take many years for chain reactions to affect the integrity of ice racks. But there is one warning. Ponds that are close to each other and deepen quickly can destroy the integrity of the ice."
"There is a speed limit in the study that shows that the ice shelf cannot collapse ridiculously fast," said co-author Alison Banwell, a glaciology researcher at the University of Colorado Boulder. "However, if it gets so covered in lakes with warm waters as fast as Larsen B was, it could collapse in a similar fashion." She added: "Multiple hydrofracture chains originating from different areas of the ice shelf can also cause the ice shelf to collapse."
The researchers published their results in the journal Geophysical Research Letters for October 24, 2019. The research was funded by the National Science Foundation and the Cooperative Institute for Environmental Research at CU Boulder. An unrelated recent study reports a record number of Antarctic meltwater reservoirs.
"Currently, there are almost no ponds on any Larsen B shelf, but much melted water weighs on ice shelves and contributes to their damage," said Banwell, who helped pioneer research on the ice shelf hydrofracture. 19659011] Transformation of the Antarctic Melting Basin for Ice Shelf and Sea Levels ” title=”The study’s principal investigator Alex Robel observes ice fracture patterns caused by wavy water in a test tank at his lab at the Georgia Institute of Technology. Credit: Georgia Tech / Allison Carter”/>
Principal Investigator Alex Robel monitors ice breakage patterns caused by wavy water in a test tank at his laboratory at the Georgia Institute of Technology . Credit: Georgia Tech / Allison Carter
Questions and Answers
The broken ice shelves themselves do not add much to the sea level. So why care?
Ice shelves float in the ocean, where they already contribute to sea level, so that when they fall apart or melt, they do not add much to it. But many ice racks repel glaciers on land that raise sea levels as they enter the ocean.
With the disappearing shelf, the velocity of the glacial stream can jump from four to ten times. The glaciologists were not aware of this until Larsen B, which was a kilometer (0.62 miles) thick with a surface area of 3,250 square kilometers (1,250 square miles), split within weeks and the glacial flow behind it jumped.
"In our scientific field, I thought ice shelves were not too important, then Larsen B. showed us that this was wrong. Reinforcing ice shelves is really what stabilizes glaciers. Few problems are more significant than those, who are considering this study, "said Brent Minchev, an assistant professor of geophysics at MIT.
Minchew did not participate in the study but has recently published another study related to it. The MIT study rules out an absolutely nightmarish scenario for the rapid destruction of the glacier due to the disappearance of the ice shelves. But he and other researchers reiterated that the glacial flow nevertheless accelerates dramatically when ice racks disappear.
Also, most of Antarctica's ice shelves were probably formed during the last ice age and may take another ice age to replace them.
How does hydro-infrastructure work and how does the study model its effects?
When fusible reservoirs at the tip of ice cracks become heavy, they can hydrophase the ice.
"The water pressure is concentrated to a point called the crack tip. It tries to push the crack and make it deeper and the ice pushes back. When the water gets deep enough, it can gain and spread the crack. to the bottom of the ice shelf, "Robel said.
The water drains down into the cracks into the ocean, then the ice jumps back in, making new cracks that can also cause hydrofracture of the adjacent lakes. The study showed that this would cover only a small number of reservoirs.
Convenient for Robel, who studies the dynamics of ice in mathematics, physics, and computer science, as ice shelves are formed in them, repaired matrixes of surface depressions appear, and this is where
Robel can apply computer science modeling, called cellular vending machines – known as pixel matrix video games – for modeling hydrofracture chain reactions. The model even outputs animations that researchers have called "minesweeper plots" after the classic 1990s computer game.
Does the study mean less danger than before the glacier flow?
No, the study simply adds to the scientific knowledge, and in fact, the flow of some Antarctic glaciers has already accelerated a great deal.
"Perhaps this mechanism is not something we have to worry about much. But we must not breathe a sigh of relief, as there are many other ways to bring much ice out of Western Antarctica quickly, "Minchev said.
Perhaps the greatest potential for glacier loss is instability, where glaciers rest on earth to The Robel study, published in July, predicts that volatility is highly likely to accelerate sea level rise.
How does this study help advance the study of the glacier?
Easier is to look for the heralds of ice
" Watching the volume of water on the surface of the ice is much easier than looking for stress failures in the ice, "said Banwell, who will visit Antarctica in November to explore the thawing waters of the George IV shelf. .
Hot ocean water attacks the edges of Antarctica's ice shelves
Alexander A. Robel et al., Speed Limitation for the Demolition of Ice Shelfs by Hydrofracture, Letters for Geophysical Research (2019). DOI: 10.1029 / 2019GL084397
Georgia Institute of Technology
Antarctica Lake Transfiguration Hazards on Ice Shelves and Sea Levels (2019, October 25)
retrieved 26 October 2019
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