Antarctica Subglacial Terrain Map Reveals Hidden Landscape Beneath Ice Sheet

Scientists have created the most detailed map so far of the bedrock hidden below Antarctica’s ice sheet, revealing an intricate network of mountains, canyons, valleys and plains, along with tens of thousands of small hills. The continent-wide map is intended to sharpen forecasts of how Antarctica’s ice may retreat and affect sea levels.

The work relies on high-resolution satellite measurements and a technique called ice-flow perturbation analysis, which infers the shape and conditions of the terrain beneath ice from subtle variations at the surface. This allowed researchers to reconstruct the Antarctic subglacial landscape continuously, including areas where no direct measurements had previously existed.

Glaciologist Robert Bingham from the University of Edinburgh said understanding this hidden terrain is central to predicting ice loss. "Having the most accurate map of Antarctica's bed shape is crucial, because the shape of the bed is an important control on friction acting against ice flow, which in turn we need to include in numerical models that are used to project how rapidly Antarctica's ice will flow towards the ocean, melt and contribute to global sea-level rise," said glaciologist Robert Bingham of the University of Edinburgh in Scotland, who helped lead the study published this week in the journal Science.

The new subglacial map shows that rougher ground, such as sharp ridges and peaks, can resist ice motion and slow retreat, supporting earlier studies. By resolving many more features than before, the dataset offers modelers a better way to include small-scale friction effects in simulations that explore different warming scenarios and their impact on future sea levels.

One of the most notable outcomes is the detection of more than 30,000 previously unmapped hills buried under the ice. These are defined as protrusions at least 165 feet, or 50 metres, high. Identifying so many separate ridges and knolls helps clarify how ice will move across the continent’s interior and towards its margins.

The Antarctic Ice Sheet is the largest single body of ice on the planet and contains about 70 percent of all freshwater. On average, the ice is estimated to be around 1.3 miles, or 2.1 kilometres, thick, with some locations reaching about 3 miles, or 4.8 kilometres, in thickness above the underlying rock.

Antarctica’s bedrock landscape was not shaped under ice from the start. Many valleys, mountain ranges and plains formed before the continent became glaciated more than 34 million years ago. Since then, the moving ice sheet has further carved and smoothed the terrain, leaving a complex imprint that the new subglacial map now captures in fine detail.

Antarctica ice sheet and subglacial map build on radar surveys

Antarctica was once physically joined to South America, but plate tectonics slowly pulled the continents apart. Over millions of years, large plates of the Earth’s crust drifted, opening ocean gateways and helping conditions that allowed a massive ice sheet to spread across the land now known as Antarctica.

Lead author Helen Ockenden, a glaciologist at the Institut des Geosciences de l'Environnement in France, noted that earlier maps mainly relied on radar instruments mounted on aircraft or pulled by vehicles. "But these surveys often have gaps of 5 km (3.1 miles) or 10 km (6.2 miles) between them, and sometimes up to 150 km (93 miles)," Ockenden said.

The new approach reduces those gaps by combining physics-based modelling with satellite data. Ockenden explained that the method "is really exciting because it allows us to combine the mathematics of how the ice flows with high-resolution satellite observations of the ice surface, and say what the landscape beneath the ice must look like everywhere across the whole continent, including in all those survey gaps. So we really gain a much more complete idea of how all the landscape features connect together."

The research team expects their Antarctica ice sheet and subglacial map to be used widely in models that test possible future sea-level change. The dataset is also likely to feed into assessments by the IPCC, the UN Intergovernmental Panel on Climate Change, which supplies evidence-based information for governments designing climate and coastal protection policies.

With inputs from WAM