Researchers predict extensive ice loss from Totten glacier
A new study published in the journal Nature, scientists from Imperial College London and institutions in Australia, the US, and New Zealand have revealed that the Totten Glacier in East Antarctica has an unstable area that could collapse and contribute to more than two metres of sea level rise beyond what is generally predicted if climate change remains unchecked.East Antarctica is the world’s largest area of ice and, until recently, was thought to be more stable than the smaller West Antarctic ice sheet.The Totten Glacier, in particular, has rapidly become recognised as the most vulnerable of all the East Antarctic glaciers, with its floating ice shelf already in retreat.Totten Glacier drains one of the world’s largest areas of ice, on the East Antarctic Ice Sheet and is currently thought to be relatively stable in the face of global warming compared with the much smaller ice sheet in West Antarctica, but Totten Glacier is bucking the trend by losing substantial amounts of ice. The new research reveals that Totten Glacier may be even more vulnerable than previously thought.Their study looks at the underlying geology of the glacier and reveals that if it retreats another 100 – 150 km, its front will be sitting on an unstable bed and this could trigger a period of rapid retreat for the glacier. This would cause it to withdraw nearly 300 km inland from its current front at the coast. Retreating the full 300 km inland may take several hundred years, according to co author Professor Martin Siegert and Co Director of the Grantham Institute at Imperial College London.
However, once the glacier crosses the threshold into the unstable region, the melting will be unstoppable, at least until it has retreated to the point where the geology becomes more stable again.”The evidence coming together is painting a picture of East Antarctica being much more vulnerable to a warming environment than we thought,” he said. “This is something we should worry about. Totten Glacier is losing ice now, and the warm ocean water that is causing this loss has the potential to also push the glacier back to an unstable place.””Totten Glacier is only one outlet for the ice of the East Antarctic Ice Sheet, but it could have a huge impact. The East Antarctic Ice Sheet is by far the largest mass of ice on Earth, so any small changes have a big influence globally.”The researchers studied patterns of erosion left by past ice sheet activity by mapping the topography of the land under the ice, and the thickness of its sedimentary rocks, which get eroded with glacial activity.”While traditional models haven’t suggested this glacier can collapse, more recent models have,” said Dr Alan Aitken of the University of Western Australia, co-author of the study.Dr Aitken and colleagues have carried out the first study to analyse the stability of the Totten Glacier’s ice sheet.
“We confirm that collapse has happened in the past, and is likely to happen again if we pass a tipping point, which would occur if we had between 3 and 6 degrees of warming above present.”Then the main problem would be that it would expose the unstable section of the ice sheet to warm sea water and this section could collapse relatively rapidly in a matter of decades, adding an extra 1.5 metres, Dr Aitken said.”We would reach a tipping point.” he said.He said the good news is that this scenario could be avoided if we limit global warming to 2 degrees above present levels.”We have in this system at least a little bit of breathing space to cope with some temperature increase because of that stable zone,” he said.”But if we exceed that point, then we’re looking at a large additional contribution that could have been avoided if we stuck to our target.”Beyond this was a 200 kilometre wide unstable area that sloped down away from the sea. This would allow melted ice to pool at the bottom of the ice sheet and encourage its rapid melting.To uncover the history of Totten Glacier’s movements, the team looked at the sedimentary rocks below the glacier using airborne geophysical surveys. From the geological record, influenced by the erosion by ice above, they were able to understand the history of the glacier stretching back millions of years.