Fate of ‘sleeping giant’ East Antarctic ice sheet ‘in our hands’ – study ice

The fate of the world’s largest ice sheet is in human hands, a new analysis suggests. The vast East Antarctic ice sheet should remain stable if global warming is limited to 2 degrees Celsius, but melting could raise sea levels by meters if the climate crisis causes temperatures to rise.

The East Antarctic Ice Sheet (EAIS) holds the vast majority of glacial ice on Earth. If all melted, sea levels would rise by 52 meters. It was thought to be stable but is now showing signs of fragility, the scientists said.

EAIS is much larger than the West Antarctic Ice Sheet (WAIS), which hosts the so-called “doomsday” Thwaites Glacier, which has lost significant stability. The total loss of WAIS would result in a 5-meter rise in sea level.

Sea levels are rising faster today than they have been in at least 3,000 years, as the seas expand as they heat up as mountain glaciers and the Greenland ice sheet melt. Even a few meters of sea level rise would redraw the world map, with profound implications for millions of people in coastal cities from New York City to Shanghai.

Scientists have warned in 2021 that the Greenland ice sheet, which could lead to a 7-meter rise in sea levels, is on the verge of a tipping point after which accelerated melting is inevitable. While the full effects of ice melt have been felt for centuries, researchers warn that carbon emissions levels over the next few decades will lock in future sea level rise.

Sea level rise on East Antarctic ice sheet can be avoided by keeping global warming below 2 degrees Celsius

The analysis shows that keeping global warming below 2C, the cap agreed by countries around the world in the 2015 Paris climate agreement, would result in EAIS contributing less than 0.5m to sea level rise by 2300. But continued high emissions and temperature rises well above 2C will result in a rise of 1.5 to 3 meters by 2300 and 5 meters by 2500.

“The fate of EAIS is still largely in our hands,” said Professor Chris Stokes of Durham University, UK, who led the research. “This ice sheet is by far the largest on Earth and it is very important that we do not wake up this sleeping giant. We used to think that the ice sheet in East Antarctica is less susceptible to climate change than West Antarctica or Greenland. impact, but we now know that some areas are already showing signs of ice loss.”

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In March, the Conger Ice Shelf in East Antarctica collapsed in what scientists said was a “sign of what’s to come”. In 2018, scientists discovered that an eighth of the glaciers that span the East Antarctic coastline are being melted by warming waters.

The new analysis, published in the journal Nature, assessed the sensitivity of EAIS to global warming, using data on past responses to rising global temperatures, information on changes happening now, and insights into possible future changes. computer simulation.

There is still a lot of uncertainty, which means that in a worst-case scenario, EAIS alone could lead to a sea level rise of more than 5 meters. In the best-case scenario, EAIS may actually accumulate more ice from snowfall than it loses, meaning it lowers sea levels slightly.

Professor Andrew McIntosh from Monash University in Australia, who was not involved in the research, said: “Vast areas of East Antarctica remain understudied, including the most vulnerable basins that could contribute to sea level rise in the coming centuries.”

“Our emissions choices will lead to a very different future world,” McIntosh said. “Society needs to understand that one of the biggest potential impacts of global warming — the widespread loss of East Antarctica’s ice — is possible if the climate warms by more than about 2 degrees Celsius.”

The analysis included data from geological history showing that the last time atmospheric carbon dioxide concentrations were higher than today was about 3 years ago. Temperatures were 2-4 degrees Celsius warmer at the time – within the range the world is likely to experience later in the century – and sea levels ended up being 10-25 meters higher than they are now. Just 400,000 years ago, when global temperatures were only rising by 1-2 degrees Celsius, parts of the EAIS retreated 700 kilometers inland.

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Professor Nerelli Abram, co-author of the ANU analysis, said: “An important lesson from the past is that the East Antarctic ice sheet is highly sensitive to even relatively mild warming scenarios. It is not as stable as we once thought. and protected.

“We now have a very small window of opportunity to rapidly reduce our greenhouse gas emissions, limit global temperature rise and protect the East Antarctic ice sheet,” she said.

EAIS is considered stable because it sits mostly above sea level, which means warming oceans can’t reach it, and the only melting comes from warmer air, which is a much slower process. In contrast, WAIS is located below sea level. However, Stokes said: “In the past decade or so, we’ve started to see the first twitches of the EAIS, with some glaciers retreating and thinning.”

Taking into account mountain glaciers and all ice sheets, the Intergovernmental Panel on Climate Change expects sea levels to rise by 0.28m to 1m by 2100, depending on emissions.

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