The Totten Glacier region in East-Antarctica is the outlet for one of the biggest ice catchments in the world. Scientists have discovered that two unstable regions exist across which the ice has retreated and advanced rapidly before in Earth history. A retreat past these unstable regions could cause a dramatic further retreat of the glacier with an associated global sea-level rise of 2 or even 4 meters.
The research published in the journal Nature 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, New Zealand, 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 waters 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 150 km 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 350 km 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 kilometers 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 350 km 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. This research contributes to a better understanding of the consequences of climate change on this region
Source: Australian Antarctic Division