NASA said on September 28, 2026 that a newly developed mapping method has produced what it calls the most detailed and accurate view yet of the bedrock beneath the Greenland Ice Sheet, revealing an expansive network of buried valleys. Researchers manually mapped 1,943 subglacial valleys, about a third of them newly identified, in a NASA-led paper published in Geophysical Research Letters.
How the method works
According to NASA, the map was derived from a technique called Ice Flow Perturbation Analysis. As ice flows over a valley or ridge, the topography leaves a faint signature on the ice surface; satellites map that surface in fine detail, and scientists use the subtle bumps and dips to infer the shape of the landscape buried below.
NASA said the work aims to improve future versions of BedMachine Greenland, a high-resolution dataset of the terrain beneath the ice sheet. The Earth Observatory post lists ICESat-2's ATLAS instrument and a model among the sources for the imagery.
The agency noted that Greenland's ice sheet spans 1.7 million square kilometers (656,000 square miles) and measures more than 3 kilometers (1.9 miles) at its thickest point, covering a landscape human eyes have never seen directly.
What the map shows
About half of the valleys already included in BedMachine Greenland, primarily near the ice sheet's edge, are now known to extend farther inland than that map indicates, in some cases by hundreds of kilometers, NASA said.
Many valleys appear to begin in the southern and eastern highlands, where the ice sheet is thought to have first formed. Near the eastern highlands, the map reveals a mountain range beneath the ice with interconnected valleys and relief that increases toward the coast; NASA said these alpine-style landforms may have survived under the ice since at least the Pliocene.
Other findings are less expected. The analysis indicates numerous long, straight valleys in the west-central region, consistently aligned southwest-northeast, an orientation the study says suggests a tectonic influence creating preferential pathways for water flow and valley formation. "That's a riddle to us," said Joe MacGregor, a NASA cryospheric scientist and co-author of the study. "Greenland is justifiably usually treated as a rigid block of old rock that is simply translated as needed to accommodate the motion and interactions of other tectonic plates."
The relatively wide angles at which the valleys branch suggest surface water did not act alone, according to the study: a widespread groundwater network, seeping upward and eroding surrounding rock, likely helped carve the valleys before the ice sheet formed.
Why it matters for the ice sheet's future
NASA said ice flow concentrates in valleys, forming glaciers that calve into fjords at the ice sheet's periphery, in a reinforcing cycle: ice funneling through a valley gets thicker, thicker ice flows faster, and faster flow carves the valley deeper. MacGregor compared western Greenland's glacially incised landscape to Yosemite, describing the coast as "El Capitan after El Capitan."
Because the relationship between ice flow and valleys is well understood, scientists expect flow to keep concentrating where valleys already are as the ice sheet retreats. "The better we understand the topography now," MacGregor said, "the better sense we'll have of what it will look like in the longer term—beyond the next decade or two—as faster ice flow propagates into Greenland's interior."
The research is published as Chartrand, A. M., et al. (2026), A Vast Valley Network Beneath the Greenland Ice Sheet, Geophysical Research Letters, 53 (13), e2026GL122028.
Key facts and where they come from
- Researchers manually mapped 1,943 subglacial valleys, roughly a third newly identified.
researchers manually mapped 1,943 subglacial valleys beneath the Greenland Ice Sheet, about a third of which are newly identified
- About half of BedMachine Greenland's valleys extend farther inland than mapped, sometimes by hundreds of kilometers.
About half of the valleys included in BedMachine Greenland, primarily near the ice sheet's edge, are now known to extend farther inland than that map indicates, in some cases by hundreds of kilometers.
- The map came from a method called Ice Flow Perturbation Analysis, which infers bedrock shape from ice-surface features.
The map, shown above, was derived from a method called Ice Flow Perturbation Analysis.
- The Greenland Ice Sheet spans 1.7 million square kilometers and is more than 3 kilometers thick at its thickest point.
Greenland is capped with a vast ice sheet that spans 1.7 million square kilometers (656,000 square miles) and measures more than 3 kilometers (1.9 miles) at its thickest point.
- The findings were published in Geophysical Research Letters by Chartrand et al.
Chartrand, A. M., et al. (2026) A Vast Valley Network Beneath the Greenland Ice Sheet. Geophysical Research Letters, 53 (13), e2026GL122028.