Last updated March 28, 2018 at 1:30 pm
New measurements bring bad news about a gigantic Antarctic glacier.
Much of the Totten Glacier – an enormous Antarctic ice structure more than twice the size of the Australian state of Victoria – has been found to be floating on the sea rather than resting on bedrock.
The surprise discovery, made by a team of scientists led by glaciologist Ben Galton-Fenzi, means the melting glacier may be at a greater risk of melting due to increasing ocean temperatures, and contribute more to global sea level rise than previously thought.
The glacier is one of the fast-moving in Antarctica and drains a major part of the East Antarctic ice sheet, an area of approximately 538,000 square kilometres. Given its importance in the region, scientists have been keeping an eye on it for several years, discovering in 2012 that it is thinning quite rapidly. A separate study published around the same time found that this thinning was being driven by warmer, deep water currents circulating through a huge cavity in a section of the ice shelf floating in the ocean.
At the time, the scientists concluded that if the thinning trend continued it would destabilise not only the Totten Glacier but the surrounding area, potentially leading to a large-scale melt and a consequent local sea level rise of up to 3.5 metres.
That already grim prediction may now have to be taken more seriously, according to the new findings.
Galton-Fenzi, of the Antarctic Climate and Ecosystems Cooperative Research Centre in Tasmania, has just returned after spending several months on the ice in Antarctica studying the Totten.
While there he worked with scientists from the University of Tasmania and the Central Washington University in the US to create a better picture of the geomorphology of the ice.
One of his colleagues, American Paul Winberry, employed seismic shockwaves to determine the structure below the surface of the Totten.
“A hammer-generated seismic wave was used to ‘see’ through a couple of kilometres of ice,” he explained.
“In some locations we thought were grounded, we detected the ocean below indicating that the glacier is in fact floating.”
The discovery, he adds, might explain recent measurements that have indicated the rate of ice-thinning is increasing. With more of the glacier in direct contact with a warming ocean, the glacier may be melting and flowing at an increased rate, as well as being more sensitive to future climate variations than thought.
“Since the 1900s the global sea-level has risen by around 20 centimetres and by the end of the century it’s projected to rise by up to one metre or more, but this is subject to high uncertainty which is why studying glaciers such as the Totten is important,” says Galton-Fenzi.
“These precise measurements of Totten Glacier are vital to monitoring changes and understanding them in the context of natural variations and the research is an important step in assessing the potential impact on sea-level under various future scenarios.”
Before returning from their mission, the researchers set up instruments that will measure changes in the glacier over the next 12 months, providing another tranche of much-needed data.