May 31, 2023

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The world's largest ice sheet threatens to melt and threatens sea level rise

The world’s largest ice sheet threatens to melt and threatens sea level rise


Scientists say the window to protect the world’s largest ice sheet from significantly shrinking is dwindling, with worrying new predictions that it has the potential to unleash sea-level rises of up to 16 feet in the long term if greenhouse gas emissions targets are not met.

The vast ice sheet in East Antarctica, It is roughly the size of the United States, It used to be considered less vulnerable to climate change than the Greenland and West Antarctic ice sheets – many glaciers are losing ice as quickly as they are. Undermined by warm ocean waters. Although, in recent years, research has been It’s starting to look tough This view.

Last studypublished in Nature, combined recent findings on potential bedrock vulnerabilities and seafloor topography—particularly in areas where glaciers interact with warm waters—with an analysis of warm periods in Earth’s past.

The team of researchers from Australia, Britain, France and the United States found that if increases in global temperatures are below the upper limit set by the 2015 Paris climate agreement – two degrees Celsius above pre-industrial levels – that means the ice sheet is adding less than half. meters (1.6 ft) to sea level by the year 2500. Any increase above this temperature has the potential to raise sea levels by as much as 5 meters (16.4 feet) during the same period.

“The choices we make today in terms of emissions reductions will be determined by whether East Antarctica will remain largely dormant as a very large ice cap, or if we start implementing some unstoppable changes that will add to the fact that it will continue to do so,” said Nereli Abram, a climate scientist at the university. Australian national and study co-author, in an interview: “The problem of sea level rise we are already facing.”

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UN Secretary-General Antonio Guterres warned earlier this year that the most ambitious target set out in the Paris Agreement – to limit global temperature rise to 1.5°C (2.7°F) above pre-industrial levels – is On life support.

Evidence from seafloor sediments around East Antarctica suggests that part of the ice sheet collapsed and contributed to sea levels increase by several meters during the mid-Pliocene, about 3 million years ago, when temperatures were about 2 to 4 million years higher, the researchers said. degrees Celsius. from now on. Nearly 400,000 years ago, there is evidence that part of the ice sheet retreated more than 400 miles inland, at a time when the temperature was more than 2 degrees Celsius more than it is now.

Scientists have just discovered a massive new weak spot in the Antarctic ice sheet

“The main lesson from the past is that the East Antarctic ice sheet is very sensitive to even relatively modest warming scenarios. It is not as stable and protected as we previously thought,” Abram said.

Chris Stokes, a professor of geography at Britain’s University of Durham and lead author of the study, said satellite observations indicate that the ice sheet is shrinking and retreating, particularly when glaciers are in contact with warm ocean currents.

This ice sheet is the largest on the planet, containing the equivalent of 52 meters [171 feet] from sea level and it’s really important that we don’t wake this sleeping giant.”

Nick Guledge, a glaciologist at the Antarctic Research Center in Wellington, New Zealand, who was not involved in the study, said the real concern for East Antarctica is the period beyond what the research paper considers. Even as greenhouse gas emissions decrease or stop, the amount of trapped heat will set back for millennia, as the ocean continues to absorb heat from the atmosphere.

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“The past warm periods mentioned in the paper help with these conclusions, but the uncertainties remain very high,” he said.

Australian scientists are embarking on a campaign over the next few years to deepen their understanding of the Denham glacier, a 12-mile-wide glacier that flows over the deepest subsea valley in the East Antarctic Ice Sheet. Scientists have already warned That the valley could provide a potential path for the ocean to infiltrate deep into the center of Antarctica.

“We understand the Moon better than East Antarctica. Matt King, co-author of the latest study and responsible for expert Sea level and ice sheet change at the University of Tasmania.

Chris Mooney contributed to this report.