Extract from ABC News
Updated
Warm water is likely to increasingly displace cold
water around the Antarctic coastline, prompting accelerated ice melt and
more sea level rise, according to new Australian research.
Scientists
from the University of New South Wales (UNSW) have modelled how
shifting wind patterns can drag warm water currents right up to the base
of the giant ice shelves."What you usually have is cold water sitting next to the ice shelves at about minus 2 degrees Celsius and then warm water further out," said Paul Spence from the Climate Change Research Centre at UNSW.
"We found by using projected wind forces to the end of this century that warm waters tend to flood onshore, right next to the grounding lines of the glacial ice sheets."
The researchers found the warm water can be 4 degrees warmer than the cold water it displaces.
"It could lead to a massive increase in the rate of ice sheet melt, with direct consequences for global sea level rise," Dr Spence said.
It is the latest alarm being sounded by scientists that all is not well on the vast, icy southern continent.
Glaciologists have warned that the melting of some of the unstable ice sheets in West Antarctica is probably now irreversible, while others have recorded alarming ice loss in the more stable and vast East Antarctic ice sheets.
A team of scientists from UNSW and the Australian National University (ANU) have for the first time modelled how sub-surface ocean temperatures down to 700 metres are rapidly changing around Antarctica because of shifting wind patterns, thought to be partly due to global warming.
They were shocked by both the size and the speed of what they discovered.
"It certainly was for me a very frightening result," Dr Spence said.
"I didn't fully appreciate how sensitive this part of the ocean was to change and how ripe a situation it was for providing dramatic impacts on the ice sheets."
He says the research shows sub-surface warming at twice the rate previously thought.
It means the melting of West Antarctic ice shelves could be faster than anticipated in the recent Intergovernmental Panel on Climate Change report.
"They weren't considering the types of temperature warming that we're seeing in our model simulations around the Antarctic coastline," Dr Spence said.
Glacial loss 'not unlike an avalanche of snow'
The University of Hawaii's Professor Axel Timmerman, who has seen the research paper, says the melting of some unstable ice sheets might be irreversible."It's plausible that the mechanism revealed by this research will push parts of the West Antarctic ice sheet beyond a point of no return," he said.
"It's not unlike an avalanche of snow, where you don't quite know when it's going to happen but when it happens, it can happen quickly.Paul Spence from the Climate Change Research Centre at UNSW"
"This work suggests the Antarctic ice sheets may be less stable to future climate change than previously assumed."
But scientists cannot predict when these warm waters will trigger cascading glacial loss.
"It's not unlike an avalanche of snow, where you don't quite know when it's going to happen but when it happens, it can happen quickly," Dr Spence said.
The Australian Antarctic Division's Tas van Ommen says the effects of a rapidly transforming Antarctica are now likely to be felt this century.
"We need to bear in mind that even modest sea level rises half-a-metre to a metre is a very big change and if we are going to see estimates now of several tenths of a metre more than that by the end of this century, that's going to rapidly reshape our response to sea level rise," he said.
"What's concerning is that with a heavily populated planet it's going to reshape our coastlines in ways that matter in this century."
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