NASA scientists were startled when a recent exploratory mission revealed a huge and rapidly-growing cavity on the underside of one of Antaractica's glaciers-signaling that the ice mass has been melting much faster than experts realized.
"[The size of] a cavity under a glacier plays an important role in melting", Milillo says.
Before they made the discovery, Nasa researchers were looking for gaps between ice and bedrock at the bottom of Thwaites where ocean water flows in and melts the glacier from underneath. But even they found the immensity and speed of the void's growth surprising. They found a cavity 1,000-feet tall that was "big enough to have contained 14 billion tons of ice-and most of that ice melted over the last three years".
Thwaites Glacier alone holds enough ice above sea level to raise sea levels by more than 65cm if it was to melt.
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Thwaites has been described as one of the world's most unsafe glaciers because its demise could lead to rapid changes in global sea levels.
For Thwaites, "We are discovering different mechanisms of retreat", Millilo said. The research has shown that Thwaites Glacier is peeling off from the bedrock beneath it, meaning more of the glacier's base is exposed to warming waters.
Thwaites Glacier, curiously, isn't melting in a uniform way. In this region, as the tide rises and falls, the grounding line retreats and advances across a zone of about 2 to 3 miles (3 to 5 kilometers).
"On the eastern side of the glacier, the grounding-line retreat proceeds through small channels, maybe a kilometer wide, like fingers reaching beneath the glacier to melt it from below", Milillo said.
The complex pattern the new readings reveal - which don't fit with current ice sheet or ocean models - suggest scientists have more to learn about how water and ice interact with one another in the frigid but warming Antarctic environment.
Just this week, an icebreaker ship left Chile to begin a scientific expedition to Thwaites Glacier with the help of a number of other ships, researchers, planes, and tagged wild seals. Hopefully, the upcoming worldwide collaboration will help researchers piece together the different systems at work under and around the glacier, the researchers said.