Antarctic Glaciers Are Unstable, Can Slide Off Into Sea

James Marshall
Июля 10, 2019

The researchers found a precise estimate of how much ice the glacier would shed in the next 50 to 800 years was not possible due to unpredictable climate fluctuations and data limitations. However, 500 simulations of different scenarios pointed to it losing stability.

"If you trigger this instability, you don't need to continue to force the ice sheet by cranking up temperatures".

Assistant professor Alex Robel, who led the study on Antarctica's ice melt at Georgia Tech's School of Earth and Atmospheric Sciences, warned of the consequences.

"After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years", Hélène Seroussi, an author of the study and a NASA scientist, said in a press release. "That will make for a sea-level rise of about half a meter (1.64 feet)", Seroussi added within the statement.

A complete loss of the West Antarctic ice sheet would be expected to increase global sea levels by about five metres (16ft), causing coastal cities around the world to become submerged.

Researchers from the Georgia Institute of Technology, Nasa Jet Propulsion Laboratory, and the University of Washington made a number of computer generated models to predict the glaciers rate of decline.

The Antarctic study was funded by the National Science Foundation and space agency NASA.

That is particularly relevant to the challenge of engineering against flood dangers.

While scientists worry about the Arctic permafrost melting and exposing ancient microbes and contributing to the sea level rise, many experts fear that unstable Antarctic glaciers could result in even faster sea level rise.

Most of that water is frozen in masses of ice and snow that can be up to 10,000 feet (3 kilometres) thick.

When this happens, it would be impossible to stop it from flowing into the ocean, which could trigger a significant rise in sea levels.

The ice above the hollow eventually loses land contact and flows even faster out to sea.

The Antarctic ice sheet has more than 50 times the amount of ice than the mountain glaciers in the world combined, and eight times as much ice in the Greenland ice sheet, Robel added in the statement.

And once the "instability" begins, nothing could prevent the ice from melting completely - potentially drowning some low-lying areas of coastline. In spots where the bedrock underneath the ice behind the grounding line slopes down, deepening as it moves inland, the instability can kick in.

"As more heat and water get under the glacier, it melts faster". This is perhaps the most worrying process from a sea-level perspective: these bits of ice eventually melt in the wider ocean, but the process also speeds up the rate at which glaciers slide into the waters (as they're no longer buoyed up by the ocean), leading to more and more melting.

Antarctica is ringed by a skirt of ice sheets and floating ice shelves that create a physical barrier between the ocean and the landlocked ice on the continent.

How did the researchers integrate instability into sea level forecasting? Normally, when climate conditions fluctuate strongly, Antarctic ice evens out the effects. Ice flow in such conditions will increase gradually, not wildly, but the instability produced the opposite effect in the simulations.

But Dr Robel added: "The system didn't damp out the fluctuations, it actually amplified them".

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