The enormous Thwaites Glacier, a rapidly changing outlet of the West Antarctic Ice Sheet, is not only being eroded by the ocean it’s being melted from below by geothermal heat.
The findings by the Institute for Geophysics at The University of Texas at Austin change the understanding of conditions beneath the West Antarctic Ice Sheet where accurate information has previously been unobtainable.
The Thwaites Glacier has been the focus of considerable attention in recent weeks as other groups of researchers found the glacier is on the way to collapse.
However, more data and computer modeling are needed to determine when the collapse will begin in earnest and at what rate the sea level will increase as it proceeds.
Using radar techniques to map how water flows under ice sheets, the researchers were able to estimate ice melting rates and identify significant sources of geothermal heat under Thwaites Glacier.
They found these sources are distributed over a wider area and are much hotter than previously assumed.
The geothermal heat contributed significantly to melting of the underside of the glacier, and it might be a key factor in allowing the ice sheet to slide, affecting the ice sheet’s stability and its contribution to sea level rise.
The cause of the variable distribution of heat beneath the glacier is thought to be the movement of magma and volcanic activity arising from the rifting of the Earth’s crust beneath the West Antarctic Ice Sheet.
Knowledge of the heat distribution beneath Thwaites Glacier is crucial information which enables scientists to more accurately predict the response of the glacier to the presence of a warming ocean.
Until now, scientists had been unable to measure the strength or location of heat flow under the glacier. Current ice sheet models have assumed that heat flow under the glacier is uniform like a frying pan with even heat distribution across the bottom of the ice.
The findings of lead author Dusty Schroeder and his colleagues show that the glacier sits on something more like a multi-burner stove with burners putting out heat at different levels at different locations.
“It’s the most complex thermal environment you might imagine,” said co-author Don Blankenship, a senior research scientist.
“And then you plop the most critical dynamically unstable ice sheet on planet Earth in the middle of this thing, and then you try to model it. It’s virtually impossible.”
The Thwaites Glacier is the size of the US state of Florida, is up to 4,000 meters thick and is considered a key question mark in making projections of global sea level rise.
The glacier is retreating in the face of the warming ocean and is thought to be unstable because its interior lies more than two kilometers below sea level while, at the coast, the bottom of the glacier is quite shallow.
The collapse of the Thwaites Glacier would cause an increase of global sea level of between 1 and 2 meters, with the potential for more than twice that from the entire West Antarctic Ice Sheet.
The new findings are reported in the PNAS (Proceedings of the National Academy of Sciences),
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