Antarctica, the Earth’s landmass now most synonymous with bad news, has a new feature for us to worry about.

A team of scientists from the UK, Denmark, the Netherlands, and Norway just discovered three canyons hidden beneath hundreds of feet of ice in interior Antarctica. In a paper published this month in the journal Geophysical Research Letters, they write that the canyons are in the region where the East and West Antarctic Ice Sheets meet, and the deep subterranean grooves are channelizing ice flow into the sea as the two sheets come together.

“[If] climate conditions change in Antarctica, we might expect the ice in these troughs to flow a lot faster towards the sea. That makes them really important, and we simply didn’t know they existed before now,” Kate Winter, a researcher at Northumbria University in the UK and the lead author on the paper, told the BBC.

The Antarctic ice sheets are expected to keep thinning as the planet warms; it’s already happening to the ice shelves that skirt the rim of the sheets. If that happens, the resulting change in mass could trigger an acceleration of ice flow through these grooves, and could act as a feedback loop driving further ice-sheet disintegration, contributing the sea level rise.

The largest of the three canyons, which the researchers named Foundation Trough, is more than 217 miles (350 kilometers) long and 22 miles wide. That’s roughly the distance between Washington DC and New York City.

As the BBC points out, this paper is the first to come out of PolarGAP, a project of the European Space Agency to take observations of a part of the planet that its satellites cannot “see,” because they don’t orbit over the planet that far south. The PolarGAP project is flying radar-equipped planes over those places to collect data in the satellites’ stead.