Antarctica hasn’t been doing so well lately. The continent is rapidly melting, and a large chunk of the snow and ice is held back from the ocean only by an array of glaciers and ice shelves guarding the coasts. None of these are doing well, but one of them—the Thwaites Glacier in West Antarctica—is rapidly crumbling. Now scientists have learned why it’s collapsing so quickly: There’s a giant underground cavern in the glacier almost as big as Manhattan.

The data comes from NASA’s Operation IceBridge, a program that flies radar-equipped planes over the poles to map out glaciers and ice sheets in three dimensions. These radar images are even capable of seeing through the ice to get a clear model of the glacier down to the bedrock. This information is extremely useful to scientists because how quickly a glacier melts depends a great deal on what’s going on near that bedrock.

In Thwaites’ case, that radar uncovered a gigantic cavern between the glacier itself and the bedrock below it. That cavern is likely filled with air much warmer than the surrounding ice, triggering faster melting of the glacier than would happen otherwise. Thanks to this nearly Manhattan-size gap in the ice, the entire glacier along with the surrounding ice sheet will likely disappear much more quickly.

A radar image of Thwaites from 2011 to 2017. The cavern is visible as the growing red blob in the center of the image. The noisy red and blue part in the bottom corner comes from ice breaking off into the sea. NASA/JPL-Caltech

So what happens if Thwaites melts? Immediately, we'd get about 2 feet of sea level rise. But the real danger is what happens after. Thwaites holds back a large portion of the West Antarctic Ice Sheet and a handful of nearby glaciers; if Thwaites disappears, we could see an additional eight feet of sea level rise from these sources, on top of the two feet from Thwaites itself.

Even more worrying to scientists beyond the cavern's existing is how quickly it appeared. The cavern first appeared in 2012 and most of the ice that once occupied it melted in the last three years. Most models of the Thwaites glacier don’t take into account rapid cavern forming, so the entire glacier is likely to be melting much faster than our predictions estimate.

In other words, there’s a good chance we could be looking at some serious melting in the near future, thanks to this glacier and the ice around it.

Source: NASA

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