A new study published in the journal Geology has revealed a hidden factor that could dramatically accelerate ice loss in Greenland. Scientists from the University of California, San Diego (UCSD) have mapped an invisible layer beneath the ice sheet that changes the way glaciers move and melt. This discovery reshapes how researchers understand Greenland’s contribution to sea-level rise, pointing to processes occurring deep below the surface that could determine the planet’s future coastlines.
Using seismic waves generated by earthquakes, UCSD scientists led by Yan Yang analyzed Greenland’s subsurface beneath kilometers of ice without drilling. By measuring small delays in the way these waves traveled through the Earth, the team constructed a map of the ground beneath the ice sheet. What they found suggests that Greenland’s foundation is far more complex and dynamic than previously thought.
The study points to a mosaic of conditions beneath the ice: some regions are rigid and stable, while others appear more fluid and changeable. These hidden differences can dramatically influence the speed at which glaciers slide toward the ocean. The findings reveal that Greenland’s ice does not simply melt from the top down, but also moves in response to what lies beneath. Where the base is smoother or less resistant, the immense weight of the ice sheet allows it to flow more rapidly toward coastal areas. This movement feeds outlet glaciers, which transport enormous amounts of ice into the sea.
Scientists also observed that temperature and meltwater interact with these subsurface layers. During warmer months, meltwater can penetrate deep through moulins, or vertical shafts, reaching the base of the ice sheet. Once there, it alters the pressure balance between the ice and the ground, influencing how easily the ice can slide. The findings suggest that the relationship between heat, water, and subsurface material plays a greater role in ice flow than previously acknowledged. This means that parts of Greenland that appear stable from space may, in fact, be poised for rapid change. As the Arctic continues to warm, areas that have remained stable for centuries may begin to shift, adding uncertainty to global sea-level rise projections.