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

The fate of the world’s largest ice sheet is in humanity’s hands, a new analysis has shown. If global warming is limited to 2C, the large East Antarctic ice sheet should remain stable, but if the climate crisis increases temperatures, the melting could raise sea levels by many metres.

The East Antarctic Ice Sheet (EAIS) contains the vast majority of Earth’s glacier ice. Sea level would rise 52 meters if everything melted. It was thought to be stable but is now showing signs of vulnerability, the scientists said.

The 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 the WAIS would cause 5 meters of sea level rise.

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

The Greenland ice sheet, which could lead to 7 meters of sea level rise, is on the brink of a tipping point after which accelerated melting would become inevitable, scientists warned in 2021. Although the full impact of melting ice is felt over centuries, the researchers warned that the level of carbon emissions over the next few decades will lock in sea level rise in the future.

Sea level rise from the East Antarctic Ice Sheet can be avoided by keeping global warming below 2°C

The analysis shows that keeping global warming below 2°C, the upper limit agreed by the world’s nations in the 2015 Paris climate agreement, would result in the EAIS contributing less than 0, 5m of sea level rise by 2300. But continued high emissions and temperature rise well above 2C would result in a rise of 1.5 meters to 3 meters by 2300 and up to 5 meters for 2500.

“The fate of the EAIS remains very much in our hands,” said Professor Chris Stokes of Durham University in the UK, who led the study. “This ice sheet is by far the largest on the planet and it is very important that we do not wake this sleeping giant. We used to think that the ice sheets in East Antarctica were much less vulnerable to climate change, compared to the “West Antarctica or Greenland, but now we know there are some areas that are already showing signs of ice loss.”

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In March, the Conger Ice Shelf in East Antarctica collapsed, which scientists said was “a sign of things to come”. In 2018, scientists discovered that a group of glaciers covering an eighth of the coast of East Antarctica was melting due to warming seas.

The new analysis, published in the journal Nature, assessed the sensitivity of the EAIS to global warming using data on how it responded to higher global temperatures in the past, information about changes occurring now, and simulations by computer of possible futures.

There are significant uncertainties, so the EAIS alone could lead to a sea level rise of more than 5 meters in the worst case scenario. At best, the EAIS can accumulate more ice from the snowfall than it loses, meaning it would lower sea levels slightly.

Professor Andrew Mackintosh of Monash University, Australia, who was not part of the study team, said: “Large areas of East Antarctica remain unstudied, including the most vulnerable basins that could contribute to sea-level rise in the coming centuries.”

“Our emissions choices will lead to very different future worlds,” Mackintosh said. “Society needs to understand that one of the biggest potential impacts of global warming, the widespread loss of East Antarctic ice, is possible if climate warming exceeds 2C.”

The analysis includes data from the geological past showing that the last time CO2 concentrations in the atmosphere were higher than today was about 3 years ago. Temperatures were then 2 to 4 degrees Celsius higher, in the range the world could experience by the end of this century, and sea levels eventually rose 10 to 25 meters higher than they are today. As little as 400,000 years ago, part of the EAIS retreated 700 km inland when the global temperature rose by only 1-2ºC.

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Professor Nerilie Abram, co-author of the analysis at the Australian National University, said: “A key lesson from the past is that the East Antarctic ice sheet is very sensitive even to relatively warm scenarios It is not as stable and protected as we once thought.

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

The EAIS was thought to be stable because much of it is above sea level, meaning that warming oceans cannot reach it and the only melting is from the air more warm, which is a much slower process. Instead, the WAIS is below sea level. However, Stokes said: “Over the last decade or so, we’ve started to see the first contractions of the EAIS, with some glaciers retreating and thinning.”

Taking into account mountain glaciers and all ice caps, the Intergovernmental Panel on Climate Change projects between 0.28 meters and 1 meter of sea level rise by 2100, depending on emissions.

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