An underwater robot verified the worrying melting of ice beneath Antarctica

Scientists have found new clues about how it is thawing.

19 de February de 2023 11:17

A photo shows the Icefin robot operating under sea ice during a practice session near McMurdo Station in Antarctica.

Thanks to an underwater robot placed in Antarctica beneath a rapidly melting ice shelf, scientists have found new clues about how it is thawing. The findings will help determine the threat this and other ice shelves pose to the environment. long-term sea level rise.

The researchers noted that the overall melting of the underside of part of the Thwaites Glacier shelf in West Antarctica was less than expected based on calculations from computer models. But they also found that the rapid melting was happening in unexpected places: in a series of terraces and cracks that extended into the ice.

These findings do not change the fact that the Thwaites Glacier is one of the least stable, fastest retreating ice shelves in Antarctica and one of the most concerning in relation to sea level rise. Nor do they change the forecasts that The collapse of the platform and the glacier of which it is part gives rise to an elevation of approximately 0.60 meters over several centuries.

This research “is giving us much more information about the processes that give rise to the Thwaites retreat,” said one of the scientists, Peter EDDavis , an oceanographer working at the British Antarctic Survey. These discoveries, published Wednesday in the journal Nature , will be used to refine models that forecast the long-term future of Thwaites .

The study is part of a larger investigation, the Thwaites Glacier International Collaboration, sponsored by the United States and the United Kingdom, which aims to better understand what is happening on the glacier.

A photo provided by the International Thwaites Glacier Collaboration shows members of the British Antarctic Survey team drilling a hole in the Thwaites Ice Shelf, Antarctica, to deploy instruments under the ice. (Icefin/ITGC/Schmidt via The New York Times )

The ice shelf is a floating tongue of the Thwaites Glacier , a river of ice the size of Florida that helps anchor one of Antarctica's two massive ice sheets. The waters surrounding Antarctica are warming due to climate change and As warm water runs beneath the shelf, the ice melts from below and the shelf thins. The so-called grounding line, the area where floating ice reaches the bedrock, has been receding as the shelf loses ice, and in the last two decades it moved approximately twelve kilometers inland.

The new discoveries appeared in two Nature articles: Davis was the lead author of one of them, and Britney E. Schmidt , a geophysicist at Cornell University , was the lead author of the other.

Researchers set up shop on the ice during the Antarctic summer of 2019-20, with conditions often extremely cold and windy, and used hot water to drill several holes through 609 meters of ice to the ocean below, not far away. of the ground connection line.

Davis and his team lowered instruments into the water to measure its temperature, salinity, and other characteristics. Although they found that the water was well above freezing, the slow current and the superposition of water with different levels of salinity prevented it from forming. a mixture that would have caused the heat to rise higher and more ice to melt.

Alastair Graham , an oceanographer at the University of South Florida who has studied the decline of the Thwaites ice throughout history but who was not involved in these two investigations, commented that the work of Davis 's team showed that "a lot of heat rises to the Thwaites land area.” “However, not all that ocean heat is converted into melt,” he said.

A still image from a video provided by the British Antarctic Survey shows the Icefin robot being lowered into a drilling hole on the Thwaites Ice Shelf in Antarctica. (Paul Anker/British Antarctic Survey via The New York Times)

The star of the show was the underwater robot called Icefin , which was designed, built and operated by Schmidt and his team. It is a cylinder 22 centimeters in diameter and approximately 3.6 meters long that carries cameras, sonar and other instruments , as well as thrusters to move. Schmidt slowly “operated” the device using a long cable that transmitted signals from the surface.

Icefin explored cracks and steep terraces on the underside of the ice and discovered that there was rapid melting there because the nearly vertical orientation of the sides allowed mixing and brought more heat onto the ice.

Sometimes Icefin would let researchers measure what was happening just a few centimeters away from the ice. It was amazing to see those ice faces and their orientation up close, Schmidt said, “and trying to figure it out has been a big part of the story.”

Like Davis, Schmidt said the findings offered important context for what is happening on the Thwaites Glacier . “It's not 'warm water equals X amount of snowmelt,'” he explained. “It's 'warm water plus process X involves defrosting.'

Because there is generally less melt on the lower side but Thwaites remains unstable, “this means it actually takes a lot less than we thought to throw things off balance,” Schmidt said.

“This doesn't mean things are better,” he added.“It means things are different.”

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By Agenda Malvinas

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