A team of researchers led by Jamin Greenbaum of the University of Texas at Austin has discovered two seafloor troughs that could allow warm ocean water to reach the base of Totten Glacier, East Antarctica’s largest and most rapidly thinning glacier. The discovery probably explains the glacier’s extreme thinning and raises concerns about how it will affect sea level rise.
The Totten Glacier catchment, outlined in blue, is a collection basin for ice and snow that flows through the glacier. It’s estimated to contain enough material to raise sea levels by at least 3.5 m. Image credit: Jamin Greenbaum / Australian Antarctic Division.
Totten Glacier is East Antarctica’s largest outlet of ice to the ocean and has been thinning rapidly for many years. It is approximately 65 km long and 30 km wide and contains enough ice to raise global sea levels by at least 3.5 m.
Climate change is raising the temperature of the oceans, and sea levels are predicted to rise about 1 m per century; Totten Glacier could represent a major component of this change.
“It’s only one glacier, but it’s changing now and it is significant for sea levels globally,” said team member Prof Martin Siegert of Imperial College London, UK.
“The 3.5 m rise may take several centuries to complete, but now the process has started it is likely irreversible. This is another example of how human-induced climate change could be triggering major changes with knock-on impacts that will be felt globally.”
The East Antarctic Ice Sheet was previously thought to be surrounded by colder water and so relatively stable compared to the smaller West Antarctic Ice Sheet, which is losing more than 150 cubic km of ice each year.
However, satellite data have shown that the Totten Glacier has also been thinning considerably. To investigate why, Greenbaum and his colleagues from Australia, France, and the UK, surveyed the area.
Using radar and other geophysical techniques, they obtained a map of the topographical landscape underlying the glacier where it met the sea.
Their results, published online in the journal Nature Geoscience, revealed a 5 km-wide valley running underneath the glacier capable of letting warm ocean water reach the ice base. Thin ice at the margins of ice sheets can float on the ocean, but the ice inland is grounded and in contact with the bedrock.
The valley allows warm ocean water to flow underneath a region of floating ice, exposing the grounded edge of the ice sheet to the warmth and leading to glacier melting.
“We now know there are avenues for the warmest waters in East Antarctica to access the most sensitive areas of Totten Glacier,” said Greenbaum.
“Totten Glacier and the East Antarctic Ice Sheet are a much more interesting and dynamic part of the sea level rise story than we’d previously thought,” added team member Dr Dustin Schroeder of NASA’s Jet Propulsion Laboratory in Pasadena.
“We are using computer modeling to understand whether changes in Totten Glacier could lead to changes in both adjacent and more distant places in Antarctica,” Prof Siegert said.
“While this work needs to be undertaken, the change at Totten Glacier itself is significant and concerning.”
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J.S. Greenbaum et al. Ocean access to a cavity beneath Totten Glacier in East Antarctica. Nature Geoscience, published online March 16, 2015; doi: 10.1038/ngeo2388
