The short version
- Researchers identified nearly two thousand valleys beneath the Greenland Ice Sheet using a new satellite-based analysis method.
- The findings suggest groundwater played a significant role in shaping the landscape before the ice sheet formed.
- Understanding this hidden topography is critical for predicting how ice flow will accelerate as the climate warms.
A comprehensive new map of the terrain beneath Greenland’s massive ice sheet has revealed an extensive network of valleys that previous surveys missed or failed to connect. This updated view provides the most detailed look yet at the bedrock landscape hidden under more than three kilometers of ice in some areas. The findings, published in a NASA-led study, link hundreds of fragmented features into a coherent system, offering new context for the island’s geological history and improving models of how the ice sheet may behave in the future.
The mapping effort utilized a technique known as Ice Flow Perturbation Analysis. This method relies on the subtle signatures that underlying topography leaves on the surface of the moving ice. As glaciers flow over ridges or through valleys, they create faint bumps and dips on the ice surface. Satellites capture these high-resolution details, allowing scientists to infer the shape of the buried landscape with greater accuracy than before. This approach aims to refine BedMachine Greenland, a high-resolution dataset used to understand the terrain beneath the ice.
Using this technique, researchers manually mapped 1,943 subglacial valleys. Approximately one-third of these features were previously unidentified. The study also found that about half of the valleys already included in existing maps extend much farther inland than previously thought, with some reaching hundreds of kilometers deeper into the ice sheet’s interior. This expansion of known valley systems significantly alters the understanding of the subsurface geography.
Some aspects of the new map align with established theories about Greenland’s formation. Many valleys appear to originate in the southern and eastern highlands, regions where scientists believe the ice sheet first developed. Near the eastern highlands, the data reveals a mountain range beneath the ice, characterized by interconnected valleys and increasing relief toward the coast. These alpine-style landforms may have survived under the ice since at least the Pliocene epoch, preserving ancient geological structures.
Other features present more complex puzzles for researchers. The analysis shows numerous long, straight valleys in the west-central region that are consistently aligned in a southwest-northeast direction. This specific orientation suggests a tectonic influence, creating preferential pathways for water flow and valley formation. Scientists noted that this challenges the traditional view of Greenland as a rigid block of old rock that simply moves to accommodate other tectonic plates.
The angles at which these valleys branch also provide clues about their origins. The relatively wide branching angles indicate that surface water alone did not carve them. Instead, a widespread groundwater network likely played a crucial role, seeping upward and eroding the surrounding rock before the ice sheet covered the landscape. This insight shifts the focus from purely glacial erosion to a combination of hydrological and geological processes.
Understanding these valleys is essential for predicting the future behavior of the Greenland Ice Sheet. Ice flow tends to concentrate in valleys, forming glaciers that eventually calve into fjords at the ice sheet’s edges. This creates a reinforcing cycle where thicker ice flows faster, carving the valleys deeper and accelerating further ice movement. The western coast of Greenland exhibits this glacial incision power prominently, resembling steep, carved landscapes found in other mountainous regions.
As the ice sheet retreats due to climate change, flow will likely continue to concentrate in these existing valley systems. Improved knowledge of the current topography allows scientists to better anticipate how faster ice flow will propagate into Greenland’s interior over the coming decades. This long-term perspective is vital for refining projections of sea-level rise and understanding the stability of the ice sheet beyond the immediate future.
Sources behind this briefing
Go to the original reporting
- NASA↗Uncovering the Valleys Hidden Below Greenland’s Ice
