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Scientists track the sudden disappearance of Antarctic ice shelf lake


Scientists track the sudden disappearance of Antarctic ice shelf lake

The plug is unplugged and a lot of water flows to the ocean

A global team of scientists observed the sudden drainage of a large, deep, ice-covered lake in the Antarctic ice shelf-a rare phenomenon that can be explained as an ominous sign of the future survival of the ice sheet, and the potential global ocean-rising levels .

The incident was documented in a study Just published In the magazine Geophysical Research Letters, Occurred on the Emory Ice Shelf in eastern Antarctica in the 2019 Antarctic winter. Scientists estimate that when the lake water is discharged from the bottom of 1,400 meters (4,590 feet) thick ice floes, about 600 to 750 million cubic meters of water, about twice the volume of San Diego Bay, California, suddenly drains into the ocean shelf.

The authors of the study used radar images from satellites to determine when the event occurred within a week or less in June. After the unnamed lake was drained, it was replaced by a crater-like depression on the ice, covering an area of ​​approximately 11 square kilometers (4.25 square miles). The depression called the ice funnel contains the broken remains of the ice sheet.

Laser instruments on NASA’s ICESat-2 satellite also captured the event, revealing the vertical scale of the damage. The ice surface fell into the sinkhole as high as 80 meters (260 feet). The reduction in water load also made floating ice shelves lighter, and ocean pressure caused it to bend upwards, and the surrounding environment of the lake rose by 36 meters (118 feet).

In the center, a funnel of cracked ice on the Amory Ice Shelf drains from the bottom of a large underground lake. A surface melting pool surrounds this feature. (NASA ICESat-2 image)

“We believe that the weight of the water accumulated in this deep lake has opened a crack in the ice shelf under the lake. [causing] Said Roland Warner, the lead author of the study and a glaciologist at the University of Tasmania. This process is called hydraulic fracturing and has been seen on other smaller ice shelves, but it is rarely possible to penetrate such a thick layer of ice, especially in winter. Warner said that drainage may take about three days. “The current flowing into the ocean below is like the current on Niagara Falls, so it will be an impressive sight,” he said.

Although there are many meltwater lakes and streams on the Emory Ice Shelf in the south in summer, the amount of water lost from the lake is several times the amount of meltwater input each year.Research co-author Jonathan Kingslake, a professor at Columbia University’s Lamont-Dougherty Earth Observatory, said: “This sudden event is obviously the result of decades of meltwater accumulation and storage under an insulating ice cap.” Kingslake last year Co-authored a study that warned about the many ice shelves around Antarctica May be easy to eventually disintegrate Caused by hydraulic fracturing.

Hydraulic fracturing has been involved The ice shelf collapsed suddenly In the warmer and more northerly Antarctic Peninsula, in the southern summer, meltwater will also form on the surface. In recent decades, as temperatures have increased, the surface melting of some ice shelves has intensified, and recent forecasts indicate that this trend will continue. This will increase the risk of extensive hydraulic fracturing, causing more ice shelves to collapse, which in turn will allow ice to be expelled more quickly from the grounded ice sheet behind the ice shelves, causing sea level rise.

The uplift of the surrounding environment of Amery Ice Shelf formed a new lake on the shallow arms of the original lake. In the next melting season, 2020, more than one million cubic meters of water flowed into the new lake every day for several days, and then overflowed into the tiankeng. The team measured a 20-meter (65-foot) wide melt channel that had just been cut into the funnel. It seems that the crack below also reopened briefly in the 2020 melting season.

Study co-author Helen Amanda Flick of the Scripps Institution of Oceanography said it is too early to conclude that the drainage of the lake is related to the broader warming trend in Antarctica. However, she said that with the continuous development of satellite observation capabilities and more data, researchers should be able to further understand the ubiquity of these deep lakes and how they have evolved over time.

The future of the newly formed funnel is uncertain: it may accumulate meltwater again, or discharge it into the ocean more frequently. But what is certain is that scientists will now pay close attention.

The study was also co-authored by Susheel Adusumilli and Philipp Arndt of Scripps; and Julian Spergel of Lamont-Doherty.

Material from the press release University of California San Diego with Australian Antarctic Project Partnership.




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