Humans “may have lost control” of the West Antarctic Ice Sheet – with inevitable melting from heating caused by greenhouse gas emissions set to raise sea levels throughout the following decades, a study has found.

Even if emissions are controlled to achieve the best possible scenario, melting of the ice sheet will continue to accelerate this century, at a speed three times faster than during the 20th century.

Warming oceans, that are absorbing excess heat from the atmosphere, erode the ice sheet from underneath and this effect is most pronounced on the western side of the continent.

Scientists are unsure how much this is likely to contribute towards global sea level rise but if the entire West Antarctic Ice Sheet melted it would contribute around five metres, though this scenario is seen as unlikely to happen.

East Antarctica, which contains around 95 per cent of the continent’s ice, remains stable as far as scientists can see, with a recent study finding the amount of ice has been increasing there over the past 30 years, though it is rapidly melting in the west with a net loss of around 7.5 trillion tonnes of ice.

How much this melting will contribute to rising oceans is not as well understood as other polar regions such as the Greenland glaciers.

Dr Kaitlin Naughten of the British Antarctic Survey (BAS) and lead author of the study said other research beyond her own pointed to it contributing to about one metre of sea level rise by 2100.

“It appears we may have lost control of the West Antarctic Ice Shelf melting over the 21st century,” she said, describing her findings.

“Our actions today likely will make a difference further down the line in the 22nd century and beyond, but that’s a timescale that probably none of us here will be around to see.”

The research, published in the journal Nature Climate Change, has been described by scientists as “sobering” as it points to an inevitable rising of sea levels that will likely devastate many coastal communities if they do not adapt.

Millions of people around the world live by the coast and will either have to “build around” the threat or “be abandoned”, Naughten said, adding controlling emissions would result in slower sea level rise which would give people more time to adapt.

For the current study, Naughten’s BAS team simulated four scenarios for the current century against a historic baseline of the previous one, imagining that emissions are either controlled to rein in the global temperature rise to 1.5C or 2C above pre-industrial levels or that emissions continue at a medium or high level.

Every scenario showed there would be widespread warming of the Amundsen sea, which borders West Antarctica, resulting in faster melting of the ice sheets.

Other scientists cautioned against viewing the results as absolutely conclusive as they are based on a single model, but it is in line with other similar studies.

Danny Halpin
(Australian Associated Press)