Glacial valleys along the periphery of the Greenland ice sheet are more deeply incised below sea level, and reach further inland than previously thought, concludes an article published online in Nature Geoscience. The findings suggest that Greenland’s ice sheet is more vulnerable to ocean warming and thinning than thought.

Mathieu Morlighem and colleagues combined sparse ice-thickness data from radar soundings with high-resolution ice motion data from satellites to map ice thickness and bed topography along the entire margin of the Greenland ice sheet at unprecedented resolution and precision. Specifically, they identify several hitherto unknown glacial valleys where ice is grounded several hundred metres below sea level, tens of kilometres inland from the Greenland coast.