An enormous cavity two-thirds the area of Manhattan and nearly 1,000 feet (300 meters) deep has been discovered growing under West Antarctica’s Thwaites Glacier. Considered to be the world’s most crucial glacier due to its sheer size and importance to the stability of the vast ice sheets that surround it, this vast cavern has been growing rapidly, with most of its volume having formed within the last three years, and its discovery underscores the vulnerability of Antarctica’s massive ice sheets to a steadily warming planet.

This gap between Thwaites Glacier and the supporting bedrock underneath was first detected by NASA’s Operation IceBridge survey in 2010, but the sheer magnitude of what that cavity would come to represent wasn’t realized by researchers at the time. A more complete picture of the situation underneath the glacier has been constructed using data from more sophisticated satellites that have been brought online since then. 

“We have suspected for years that Thwaites was not tightly attached to the bedrock beneath it,” explains study co-author Eric Rignot of the University of California, Irvine, and NASA’s Jet Propulsion Laboratory. “Thanks to a new generation of satellites, we can finally see the detail.”

Roughly the size of Florida, meltwater from Thwaites Glacier currently contributes to about four percent of sea level rise, but it holds enough ice to raise ocean levels by a little over 2 feet (65 centimeters) if it were to melt entirely. Thwaites also supports a number of neighboring glaciers that would represent an additional 8 feet (2.4 meters) of sea level rise–glaciers that would be under an increased threat of collapse if Thwaites itself were to slide off into the ocean.

And when it comes to how glaciers melt, the maxim of ‘as above, so below’ proves to be no less true: “[The size of] a cavity under a glacier plays an important role in melting,” warns the study’s lead author, Pietro Milillo, also with JPL. “As more heat and water get under the glacier, it melts faster,” and the cavern under the Thwaites Glacier is no exception. The cavern is large enough to have contained 14 billion tons of ice, a number that is all the more alarming considering that this volume of ice has melted from a single glacier over the span of only three years. It was also revealed last summer that Antarctica’s ice sheets are melting three times faster than they were the decade before, with the Thwaites Glacier being among the two hardest-hit ice sheets on the continent. 


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