New Maps Uncover Antarctica's Hidden Landscape Beneath the Ice

Scientists have produced a clearer picture of the landscape buried under Antarctica’s ice, revealing rigid valleys, channels, and other features that were previously hard to detect. Those hidden shapes matter because they steer ice flow and influence how quickly ice can reach the ocean. A better view of the ground beneath the ice can improve forecasts of ice loss and narrow uncertainty in sea-level rise projections. Helen Ockenden and colleagues from the University of Edinburgh created a new continent-scale map. The team combined high-resolution satellite measurements of the ice sheet’s surface, limited ice-thickness data, and a method called Ice Flow Perturbation Analysis (IFPA). Instead of depending mainly on sparse airborne surveys, IFPA leans on the physics of ice flow: subtle changes at the surface can reveal what the ice is passing over far below. Importance of Antarctica’s landscape Antarctica’s ice sheet is not a static slab. It flows – and that flow largely determines how much ice is delivered to the coast, where it can thin and add to rising seas. In many regions, fast moving ice streams act like drainage corridors for huge parts of the continent. The bedrock below is a major control. Deep troughs can funnel ice and encourage faster flow. Ridges can divert it. Basins can hold thicker ice and shape where ice accumulates or drains. The bed also affects what happens at the ice-rock interface, where sliding, meltwater, and freeze-on processes can change how easily ice moves. If the bed is mapped too smoothly, models can miss important pathways and bottlenecks. The problem is that Antarctica’s bed remains difficult to measure directly. Radar and geophysical surveys have covered large areas, but gaps remain, and coverage is uneven. That leaves some of the planet’s most important terrain for sea-level predictions only partly constrained. Antarctica’s ice surface as a clue IFPA works because the bed leaves a faint fingerprint on the ice above it. Thick ice damps out sharp features, so the surface does not mirror the bed. But as ice flows over buried valleys and canyons, the surface can sag slightly, slopes can shift, and velocities can change in ways that are physically linked to the terrain below. Satellites can detect those small signals at scale. By combining surface elevation and motion with the governing physics of ice flow, the method infers bed topography across wide regions where direct surveys are limited. The goal is not to replace field data, but to connect it, filling the spaces in between. What the new map reveals The authors report that their map resolves “mesoscale” features, roughly 2 to 30 kilometers across. That size range is a sweet spot: large enough to influence ice dynamics, but small enough that older, continent-wide products often blurred it away. With this added detail, the reconstructed bed shows deep and narrow alpine-style valleys, scoured lowlands, and extensive buried channels that can extend hundreds of kilometers. Some may be relic landforms that predate the modern ice sheet. Whether those features were carved by rivers or glaciers, they can still guide ice today, shaping where flow concentrates and how the ice sheet responds to changing conditions. A very subtle signal One striking point is that the surface imprint of bed features can be tiny. A canyon under kilometers of ice may translate into only a small dip at the surface. Yet the approach can still pick up those effects when measurements are precise and the physics is applied carefully. “It is perhaps most surprising that ultimately so much detail of the bed topography – features such as glacial valleys, hills and canyons – are captured at all in the shape of the ice surface so far above,” said co-author Robert Bingham from Edinburgh. “So much change at the surface is extremely subtle – as 3 km-thick ice passes over a subglacial canyon maybe 100 meters deep, the ice surface elevation typically only falls a handful of meters, a change that is barely noticeable when travelling over the ice surface itself.” Map improves but has limits Even a high-detail reconstruction like this rests on assumptions. Any technique that infers bed shape from ice behavior must make choices about how ice deforms internally, how much it slides at the base, and how melting and freezing behave at the ice-bed interface. Those processes vary across Antarctica and are still hard to observe everywhere. “Although Ockenden et al. provide a detailed map of Antarctica’s bedrock landscape at mesoscale, it does not represent the final word on Antarctic geography,” said geophysicist Duncan Young from the University of Texas at Austin in a related perspective. “Similar to mass conservation methods, the analysis relies on major assumptions about mechanisms that are critical for modeling ice sheet evolution, such as ice deformation, basal sliding, and melt and freeze processes at the ice-bedrock interface.” Antarctica’s hidden landscape In other words, this map should be treated as a major upgrade and a guide. It can help identify where hidden valleys and channels are likely shaping flow, and it can point to the places where additional airborne or ground surveys would most improve future models. Antarctica’s contribution to sea-level rise depends on how ice flow evolves as the climate warms and oceans change. Ice flow depends, in part, on the terrain beneath the ice. By revealing midsized structures across Antarctica’s buried landscape, the new map sharpens one of the most uncertain boundary conditions in ice sheet forecasting. That clearer foundation can improve models today and make future fieldwork smarter, by showing exactly where the next measurements will matter most. The study is published in the journal Science. —– Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com. —–