West Antarctic Ice Sheet collapse is 'unavoidable' — study

A study by the British Antarctic Society published in the journal Nature Climate Change on Monday claims, "we are now committed to the rapid increase in the rate of ocean warming and ice shelf melting over the rest of the century."

Lead author, oceanographer Kaitlin Naughten, said of the study, "Our main question here was: How much control do we still have over ice shelf melting? How much melting can still be prevented by reducing emissions? Unfortunately, it's not great news."  

Naughten said it could take hundreds of years for the shelf to melt entirely — which would produce a 1.8 meter (nearly 6 foot) rise in sea levels — but major melting appeared to be inevitable according to all of the computer simulations that she and her peers conducted.

How experts evaluated the West Antarctic Ice Sheet

Researchers looked specifically at the West Antarctic Ice Sheet that juts into the Amundsen Sea for their study and found that even if global warming could be held to the international target of just a few tenths of a degree it would have, "limited power to prevent ocean warming that could lead to the collapse of the West Antarctic Ice Sheet."

Naughten's team was the first to use high-resolution computer simulations that studied the effects of warm water melting the sheet from below, looking at four scenarios tied to different amounts of carbon dioxide released into the atmosphere — in each case they found erosion would continue unabated, meaning the sheet would eventually collapse.

Even if temperatures only rose at 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels — the study's best-case scenario — researchers say the ice would still melt at a rate three times faster than last century.

"Reducing emissions can help prevent the worst-case scenario of melting, but beyond that, mitigation has a negligible impact," said Naughten.

Collapse of West Antarctic Ice Sheet one of nine climate 'tipping points'

Researchers concentrated on the West Antarctic Ice Sheet, which is more fragile than the eastern side of the southern continent, focusing on so-called gatekeeper ice shelves that float upon the ocean while keeping glaciers in place.

Author Naughten said she avoids the word "doomed" as it is still possible that emissions and indeed warming could theoretically be halted or even reversed in the longterm, adding, "It isn't unavoidable that we lose all of it because sea-level rise happens over the very long term. I only looked at this study up to 2100."

The study suggests the change could take several hundred years to play out but Naughten pointed to the ultimate speed of transformation as a key factor. She said it would be "absolutely devastating" should it take place over just a couple hundred years, but that humanity could adapt if the change could be drawn out over a couple of thousand years.

"Coastal communities," she said, "will either have to build around or be abandoned."

Though peers not involved in the study, such as Tiago Segabinazzi Dotto of the UK's National Oceanography Centre, cautioned that results "need to be treated carefully since different models and even ensembles of the same model can give different responses," he said it nevertheless aligned with other research.

The collapse of the West Antarctic Ice Sheet was identified as one of nine climate "tipping points" in 2009. Scientists at the time said that moving beyond these environmental red lines — the collapse of various ice sheets, reversals in oceanic currents, the death of the Amazon rainforest and the collapse of boreal permafrost — would prove catastrophic for life on earth. 

js/rt (AP, Reuters)