Researchers have mapped 1,943 valleys beneath Greenland’s ice sheet, including about one-third they had not identified before. The 2026 inventory also shows that roughly half of the valleys already represented in an earlier bed map extend farther inland than previously understood. The valleys were not photographed through the ice: scientists inferred their shapes from subtle changes in the ice surface and its movement over buried terrain.
What did the 2026 map reveal?
A NASA-led team manually mapped 1,943 subglacial valleys beneath the Greenland Ice Sheet. NASA’s account of the study says about one-third were newly identified. It also reports that about half of the valleys already in BedMachine Greenland—mostly near the ice-sheet edge—extend farther inland than the existing map showed, in some cases by hundreds of kilometers. NASA’s overview of the mapping describes a broader view of a connected bedrock landscape, rather than a single newly discovered canyon.
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The map highlights long, straight valleys in west-central Greenland, including both newly mapped features and extensions of previously known ones. Near the eastern highlands, it also shows a buried mountain range connected to valleys, with the terrain becoming more pronounced toward the coast. NASA describes these as alpine-style landforms that may have persisted beneath the ice since at least the Pliocene; that age is an interpretation, not a direct observation of the valleys’ formation.
How can scientists map terrain hidden under ice?
The researchers used a method called Ice Flow Perturbation Analysis. As ice flows across a buried ridge or valley, the underlying shape can produce faint changes in the ice surface and in its motion. Satellite observations of surface elevation and ice velocity capture those patterns, which researchers use to infer the bedrock below. The team then manually mapped the valleys from that evidence.
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This is not the same as seeing every valley directly with radar. Direct bed measurements are available only in some places; the new approach extends mapping into Greenland’s slower-flowing interior, where ice-thickness observations are sparse. Earlier work along the margins used mass conservation to reconcile thickness and surface-velocity measurements, but that method cannot be applied in the same way across the interior. The 2026 study’s results therefore combine measured surface behavior with interpretation of the terrain producing it. The paper, “A Vast Valley Network Beneath the Greenland Ice Sheet,” by Allison M. Chartrand and colleagues, appeared in Geophysical Research Letters, volume 53, issue 13 (DOI: 10.1029/2026GL122028); NASA’s Technical Reports Server lists June 16, 2026, as the publication date and identifies the manuscript as accepted with final changes. NASA Technical Reports Server record.
What might the valley shapes tell us about Greenland’s past?
The authors interpret the network’s form as evidence that Greenland’s southern and eastern highlands may have been likely starting areas for the ice sheet. The branching angles and other valley features also suggest that groundwater may have helped erode the landscape before glaciation. These are deductions from landform shape, not direct evidence of ancient groundwater flow.
Many of the long, straight west-central valleys run southwest to northeast. That alignment could reflect tectonic influences, but it is not yet explained. NASA study co-author Joe MacGregor called the pattern “a riddle to us.” He noted that Greenland is usually treated as “a rigid block of old rock” that moves in response to interactions among tectonic plates, making the alignment difficult to account for.
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Could the valleys affect Greenland’s glaciers?
Bedrock topography helps channel ice flow. Ice can concentrate in valleys as outlet glaciers carry it toward fjords at the margin; as ice funnels into a valley, it can thicken and move faster, while faster flow can deepen the valley. NASA says researchers expect flow to remain concentrated in established valleys as the ice sheet retreats. Better maps of the bed may therefore improve longer-term ice-flow projections, including projections beyond the next decade or two. The study does not calculate a specific amount of future sea-level rise.
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The Greenland Ice Sheet covers about 1.7 million square kilometers (656,000 square miles) and is more than 3 kilometers (1.9 miles) thick at its thickest point, according to NASA. Those figures describe the ice sheet, not the newly mapped valleys. NASA Earth Observatory.
How the 2026 valley network differs from Greenland’s famous megacanyon
NASA reported a major northern Greenland discovery in 2013: radar analysis revealed a continuous bedrock canyon running from near the island’s center toward the Petermann Glacier fjord. The feature was reported as at least 460 miles (750 kilometers) long and locally as deep as 2,600 feet (800 meters). Researchers described it as likely older than the ice sheet and as a possible route for subglacial meltwater. It is one earlier discovery, not another name for the 2026 inventory of 1,943 valleys. NASA’s 2013 account of the megacanyon.
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That earlier result relied on radar data gathered over decades, including extensive measurements from NASA’s Operation IceBridge between 2009 and 2012. Radar waves can pass through ice and reflect from the bedrock; the return time helps estimate depth. The 2026 mapping, by contrast, uses subtle surface-elevation and velocity patterns to infer buried terrain in areas where direct thickness measurements are sparse.
Where to explore the existing Greenland bed map
NASA’s Open Data Portal catalogs IceBridge BedMachine Greenland V005, a dataset containing bed topography and bathymetry alongside surface elevation, ice thickness, and an ice/ocean/land mask. It provides access to data downloads and identifies NASA’s NSIDC DAAC as publisher. The 2026 work aims to improve future versions of BedMachine Greenland; V005 should not be treated as already containing the newly mapped valley inventory. NASA Open Data Portal: IceBridge BedMachine Greenland V005.
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