The world’s largest ice cap is in danger of melting and threatens to raise sea levels



Scientists say the window to protect the world’s largest ice cap from significant shrinkage is shrinking, with disturbing new predictions that it has the potential to trigger sea level rise of up to 16½ feet long term if the greenhouse gas emission targets are not met.

The vast East Antarctica ice sheet, which is about the size of the United States, was once thought to be less vulnerable to climate change than the ice sheets of Greenland and West Antarctica – where several glaciers have rapidly lost ice as they are undermined by warm ocean water. In recent years, however, research has begun to emerge to challenge this view.

The latest study, published in the journal Nature, combined recent findings on the potential vulnerabilities of bedrock and underwater topography – particularly in areas where glaciers interact with warm water – with an analysis of time periods. hot weather from Earth’s past.

The team of researchers from Australia, Britain, France and the United States found that if the global temperature increase is below the upper limit set by the 2015 Paris climate agreement – 2 degrees Celsius above pre-industrial levels – this should mean that the ice sheet adds less than half a meter (1.6 feet) to sea level by the year 2500. Any increase above this temperature has the potential to raise sea levels up to 5 meters (16.4 feet) over the same period.

“The choices we make today in terms of reducing emissions will fall into place, whether East Antarctica remains largely inactive as one very large ice sheet, or whether we start to set in motion irreversible changes that will add to the sea level rise problem we already face,” said Nerilie Abram, a climatologist at the Australian National University and co-author of the study. , in an interview.

Earlier this year, UN Secretary-General António Guterres warned that the most ambitious goal set out in the Paris agreement – limiting global temperature rise to 1.5 degrees Celsius (2, 7 degrees Fahrenheit) above pre-industrial levels – is “alive”.

Researchers said evidence from seafloor sediments around East Antarctica indicates that part of the ice sheet collapsed and contributed to several meters of sea level rise during the mid-Pliocene. , about 3 million years ago, when temperatures were about 2 to 4 degrees Celsius higher. that now. About 400,000 years ago, there is evidence that part of the ice cap retreated more than 400 miles inland, at a time when it was 1-2 degrees Celsius warmer than currently.

Scientists Just Discovered a Massive New Vulnerability in the Antarctic Ice Sheet

“A key 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 once thought,” Abram said.

Chris Stokes, professor of geography at Britain’s Durham University and lead author of the study, said satellite observations suggested the ice sheet was thinning and retreating, particularly where glaciers are in contact with warm ocean currents.

“This ice cap is by far the largest on the planet, containing the equivalent of 52 meters [171 feet] sea ​​level and it’s really important that we don’t wake this sleeping giant,” Stokes said in a statement.

Nick Golledge, a glaciologist at the Antarctic Research Center in Wellington, New Zealand, who did not work on the study, said the real concern for East Antarctica is the period beyond what the article considers. Even if greenhouse gas emissions decline or stop, the amount of heat locked up will set back for millennia as the ocean continues to absorb heat from the atmosphere.

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

Australian scientists are embarking on a campaign over the next few years to deepen their understanding of the Denham Glacier region, a 12-mile-wide stream of ice that flows over the deepest submarine canyon in the Australian Ice Sheet. East Antarctica. Scientists have previously warned that the canyon could provide a potential pathway for the ocean to seep deep into central Antarctica.

“We understand the Moon better than East Antarctica, so we don’t yet fully understand the climate risks that will emerge from this area,” said Matt King, co-author of the latest study and sea level change expert. and the ice cap at the University of Tasmania.

Chris Mooney contributed to this report.


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