A majorly concerning new study claims that we are seeing the West Antarctic ic shelf breaking up from the inside out, and there’s precious little time to reverse the trend. A key glacier known as the Pine Island Glacier, which is part of hte ice shelf that bounds the West Antarctic Ice Sheet, is one of two glaciers apparently undergoing a sudden retreat.

That would be a major problem for the world, flooding coastlines across the globe. And scientists say it’s really happening, with researchers from Ohio State University seeing something odd in satellite images before a huge 225 square mile iceberg broke off in 2015.

Essentailly, they saw signs that a rift had formed at the base of the ice about 20 miles inland two years prior, and then the rift moved upward until it broke the surface of the ice, indicating the ice is heating up from below.

“It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt, it’s a question of when,” said study leader Ian Howat, associate professor of earth sciences at Ohio State. “This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.

“We need to understand exactly how these valleys and rifts form, and what they mean for ice shelf stability,” Howat said. “We’re limited in what information we can get from space, so this will mean targeting air and field campaigns to collect more detailed observations. The U.S. and the U.K. are partnering on a large field science program targeted at that area of Antarctica, so this will provide another piece to the puzzle.”