To unravel the complexity, the researchers built on a previous study they published in 2013 that mapped out the system of channels that flows beneath the Thwaites Glacier, a fast-flowing glacier that scientists say is vulnerable to global warming.
Using data from airborne radar, the researchers were able to figure out where these subglacial streams were too full to be explained by flow from upstream. The swollen streams revealed spots of unusually high melt, Schroeder said. Next, the researchers checked out the subglacial geology in the region and found that fast-melting spots were disproportionately clustered near confirmed West Antarctic volcanoes, suspected volcanoes or other presumed hotspots.
"There's a pattern of hotspots," Schroeder said. "One of them is next to Mount Takahe, which is a volcano that actually sticks out of the ice sheet."
The minimum average heat flow beneath Thwaites Glacier is 114 milliwatts per square meter (or per about 10 square feet) with some areas giving off 200 milliwatts per square meter or more, the researchers report today (June 9) in the journal Proceedings of the National Academy of Sciences. (A milliwatt is one-thousandth of a watt.) In comparison, Schroeder said, the average heat flow of the rest of the continents is 65 milliwatts per square meter.
"It's pretty hot by continental standards," he said.
The extra melt caused by subglacial volcanoes could lubricate the ice sheet from beneath, hastening its flow toward the sea, Schroeder said. To understand how much the volcanic melt contributes to this flow — and what that means for the future of the West Antarctic Ice Sheet— glaciologists and climate scientists will have to include the new, finer-grained findings in their models. Schroeder and his colleagues also plan to expand their study to other glaciers in the region.
"Anywhere in the West Antarctic Ice Sheet is going to be a candidate for high melt areas," he said. "And we have radar data covering much of it."
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