Greenland is now mostly white. Snow and ice and glaciers abound, but are shrinking as the climate warms. Turns out that some of the glaciers are found in canyons and the canyons are deeper than previously thought.

Scientists at NASA and the University of California, Irvine (UCI), have found that canyons under Greenland’s ocean-feeding glaciers are deeper and longer than previously thought, increasing the amount of Greenland’s estimated contribution to future sea level rise.

“The glaciers of Greenland are likely to retreat faster and farther inland than anticipated, and for much longer, according to this very different topography we have discovered,” said Mathieu Morlighem, a UCI associate project scientist who is lead author of the new research paper. The results were published Sunday in the journal Nature Geoscience.