Research published in the prestigious journal Nature has revealed vulnerabilities deep beneath Earth’s largest ice sheet that, with a warming climate, could lead to a rise in sea level of several metres in coming centuries to millennia.

The research was carried out as part of the ICECAP airborne Antarctic Survey, which is supported by the Australian Antarctic Programme.

Australian Antarctic Division and Antarctic Climate and Ecosystems Cooperative Research Centre scientists Dr Tas van Ommen and Dr Jason Roberts worked with lead author Dr Alan Aitken from the University of Western Australia on the study, along with scientists from the Institute for Geophysics at the University of Texas at Austin, Victoria University of Wellington, NZ, and Imperial College London.

Glaciologist, Dr Roberts, said the study looked at the landscape evolution and past history of ice-sheet change of the Totten Glacier in East Antarctica, the outlet for one of the world’s largest ice catchments. The research builds on a 2015 study that discovered pathways for warm ocean to reach underneath a floating portion of the glacier, potentially making it vulnerable to retreat.

“In this study we used ice-penetrating radar, magnetic and gravity data, to determine the thickness of the ice-sheet and the sediment thickness under the ice sheet, which we then used to map glacial erosion beneath the ice sheet,” Dr Roberts said.

“We found two unstable zones across which the ice sheet appears in the past to have retreated and advanced rapidly. The nature of the bedrock hills and valleys does not provide a stable midway position.”

Dr van Ommen said while scientists knew advance and retreat of the ice had occurred in this region in the past, this was the first study to show evidence of this instability.

“If the ice retreats further than about 150km from its present position, it reaches the first of the unstable zones,” Dr van Ommen said.

“This would trigger a period of rapid retreat for the glacier, causing it to withdraw over 350km inland from its current front at the coast. Such an occurrence would contribute more than 2 meters to global sea-level rise.”

While a retreat of several hundred km inland may take several hundred years, once the glacier crosses the threshold into the unstable region, the ultimate retreat will be unstoppable — at least until it has reached the point where the bedrock highlands provide a new stable position for the ice.

If melting pushes beyond the 350km zone, this study reveals a further zone of unstable retreat that would deliver over 4 metres of sea level rise.

The Totten Glacier region is a key area for understanding the large-scale and long-term vulnerabilities of the Antarctic Ice Sheet, but until now knowledge of the region’s glacial history has been very limited.