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New analysis of the Greenland ice sheet indicates it is on the brink of a major tipping point that could see accelerated melting become inevitable.
Researchers Niklas Boers, of the Potsdam Institute for Climate Impact Research in Germany, and Martin Rypdal, from the Arctic University of Norway, based the study on a 140-year record of ice sheet height and melting rates in the Jakobshavn basin, one of the five biggest basins in Greenland.
The Jakobshavn basin is the fastest-melting of those located on the ice sheet, and rising temperatures caused by global warming have already caused trillions of tonnes of the sheet to melt and flow into the ocean.
Now, the analysis by Boers and Rypdal found warning signs that the sheet may be at a tipping point, evidenced through examination of the size and duration of changes found in temperature records, ice cores, and modelling that reconstructed the ice sheet’s elevation and melting rates.
A surge in melting is believed to be the result of a cycle in which the reduction in the height of the ice sheet exposes it to warmer air at lower altitudes, in turn paving the way for more melting.
The researchers could not determine whether the sheet is already at the point of no return, or whether the tipping point could be imminent, but if it passes the threshold there will be no saving the sheet from accelerated melting, even if world leaders manage to get a handle on global warming.
Boers told The Guardian: ‘We’re at the brink, and every year with CO2 emissions continuing as usual exponentially increases the probability of crossing the tipping point. It might have passed [the tipping point], but it’s not clear. However, our results suggest there will be substantially enhanced melting in the near future, which is worrying.’
Sea levels would rise by as much as seven metres if the entire ice sheet was to melt, but the researchers have assured that crossing the tipping point would not necessarily result in this much damage, because it might be possible for a smaller version of the sheet to remain stable.
More likely, the melting ice will result in one-to-two metres of sea level rise, though this would take place over centuries, Boers explained. Melting the entire ice sheet, meanwhile, would take a millennium.
Boers said humanity would have to strive to get temperatures back below pre-industrial levels in order to ‘get back to the original height of the Greenland ice sheet,’ noting: ‘The current and near-future ice loss will be largely irreversible.’
He added: ‘That’s why it is high time we rapidly and substantially reduce emissions from burning fossil fuels and restabilise the ice sheet and our climate.’
Boers noted the research, published in the Proceedings of the National Academy of Sciences of the United States of America, only examined one part of Greenland. However, he said it may reflect ‘something that is happening in many parts of Greenland,’ explaining: ‘We just don’t know for sure, because we don’t have the high-quality data for other parts.’
Moving forward, Boers stressed the need for better monitoring of the Greenland ice sheet to increase understanding of the feedback mechanisms that determine the current stability and future evolution of the landscape.
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