New mapping based on tiny changes in the ice surface has identified 1,943 valleys beneath the Greenland ice sheet. About a third of them did not appear on previous maps, and others are much longer than previously thought.
Beneath Greenland's thick ice sheet lies a network of valleys and ridges that cannot be observed directly. In a study published in the journal Geophysical Research Letters A team led by NASA researchers presented a detailed mapping of this landscape: the researchers manually marked 1,943 subglacial valleys, about a third of which were identified for the first time. The research findings were presented on September 28, 2026, on NASA's Earth Observatory website.
How do you map land that no one sees?
The method, called Ice Flow Perturbation Analysis, relies on precise satellite imagery of the ice surface. When ice flows over a valley or ridge, the shape of the underlying rock leaves a faint mark on the surface. From the small bumps and depressions, researchers deduce the structure of the ground. This is an inference from the ice surface data, not a direct photograph of the underlying rock; therefore, the map complements existing measurements and reconstructions, not replaces them.
The existing BedMachine Greenland map includes many of the valleys, mostly at the edges of the ice sheet. According to the new analysis, about half of the valleys shown in it extend further inland than previously marked, sometimes by hundreds of kilometers. The finding could improve our understanding of possible future ice flow paths.
Clues to the geological past
In west-central Greenland, long, straight valleys are prominent, generally trending southwest to northeast. The researchers suggest that ancient tectonic structures may have influenced their location. The wide branching angles between other valleys indicate, they believe, that groundwater also helped carve them before the current ice sheet covered the area. These are interpretations of landscape structure, not direct measurements of ancient processes.
The shape of the valleys is still important today: ice tends to concentrate in them, flow towards the coastline and feed glaciers that break off into fjords. The better we know the contours of the land, the better we can improve long-term models of the movement of the ice as it retreats. The study itself does not provide a new forecast or an up-to-date number for sea level rise. To understand the broader context, Overview of ice loss in Greenland and Antarctica Shows the ice mass changes measured in recent years.
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Sources: NASA Earth Observatory, 28.9.2026; Chartrand and colleagues, A Vast Valley Network Beneath the Greenland Ice Sheet,Geophysical Research Letters, 2026.
