Antarctic ice susceptible to climate domino effect

New study says melting of small Amundsen Basin likely to trigger a climate tipping point

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The meltdown of West Antarctica’s ice sheets is likely already under way. @berwyn photo.

Staff Report

Just a small shift in the Antarctic climate could have long-lasting consequences on a global scale, according to a new research paper that once again takes a close look at the fate of the West Antarctic Ice Sheet.

Based on the new study, destabilization of the relatively small Amundsen Basin — triggered by a few decades of ocean warming — could trigger a massive ice loss from the West Antarctica Ice Sheet that would raise global sea level by 10 feet. Other recent studies show that this area is already losing stability, making it the first element in the climate system about to tip.

“What we call the eternal ice of Antarctica unfortunately turns out not to be eternal at all,” said Johannes Feldmann, with the Potsdam Institute for Climate Research. “A few decades can kickstart change going on for millennia,” Feldmann said in a press release, describing the findings, to be published in the Proceedings of the National Academy of Sciences.

“Once the ice masses get perturbed, which is what is happening today, they respond in a non-linear way: there is a relatively sudden breakdown of stability after a long period during which little change can be found,” he said, adding that it’s a classic example of a climate tipping point.

Ocean warming is slowly melting the ice shelves from beneath. Large portions of the West Antarctic ice sheet are grounded on bedrock below sea level and generally slope downwards in an inland direction. Ice loss can make the grounding line retreat, thereby exposing more and more ice to the slightly warmer ocean water, accelerating the retreat.

“In our simulations, 60 years of melting at the presently observed rate are enough to launch a process which is then unstoppable and goes on for thousands of years,” Feldmann said. This would eventually yield at least 3 meters of sea-level rise. “This certainly is a long process,” Feldmann says. “But it’s likely starting right now.”

“So far we lack sufficient evidence to tell whether or not the Amundsen ice destabilization is due to greenhouse gases and the resulting global warming,” said co-author and IPCC sea-level expert Anders Levermann, also from the Potsdam Institute. “But it is clear that further greenhouse-gas emission will heighten the risk of an ice collapse in West Antarctica and more unstoppable sea-level rise.”

“That is not something we have to be afraid of, because it develops slowly,” concludes Levermann. “But it might be something to worry about, because it would destroy our future heritage by consuming the cities we live in, unless we reduce carbon emission quickly.”

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