There are few frontiers in the world that can still be said to be unexplored. One of these terra incognita is the land beneath Antarctica’s ice sheets. Buried under kilometres of ice is a fascinating realm of canyons, waterways, and lakes. These features have now been revealed in the most detailed picture yet of the land beneath the ice.

The new map, called Bedmap3, peels back the frozen veil of Antarctica. It is the culmination of more than six decades of surveys. Bedmap3 combines data from planes, satellites, ships, and even dog-drawn sleds to create a vivid portrait of Antarctica as if its 27 million cubic kilometers of ice had vanished.

Why Antarctica’s Bed Matters

The project, led by an international team of researchers, incorporates 84 new aerial surveys, adding 52 million data points and 1.9 million line-kilometers of measurements.

They also used advanced interpolation techniques to fill in gaps where direct measurements were lacking. For example, in areas close to rock outcrops, where ice is thin and difficult to measure, the researchers used a mathematical model based on the flow of ice to estimate thickness.

The result is a map that fills in critical gaps, particularly in East Antarctica’s deep interior and along the West Antarctic coastlines.

The volume of ice that sits atop the continent at the South Pole is staggering. Antarctica’s ice sheet holds enough water to raise global sea levels by 58 meters if it were to melt entirely. While that’s not likely to happen anytime soon, even small changes in the ice sheet’s stability could have significant consequences. This is why understanding the shape of the land beneath the ice is crucial for predicting how the ice will flow and melt in a warming world.

The new map shows that the volume of ice in Antarctica is roughly the same as previous estimates — about 27 million cubic kilometers. But the details are far more precise. For example, the map reveals the intricate topography of subglacial troughs, which guide the flow of ice from the continent’s interior to the ocean. These troughs are like rivers of ice, and their shape can determine how quickly ice moves and how vulnerable it is to melting.

“This is the fundamental information that underpins the computer models we use to investigate how the ice will flow across the continent as temperatures rise,” said Dr. Hamish Pritchard, a glaciologist at the British Antarctic Survey (BAS) and lead author of the study. “Imagine pouring syrup over a rock cake — all the lumps and bumps will determine where the syrup goes and how fast. And so it is with Antarctica: some ridges will hold up the flowing ice; the hollows and smooth bits are where that ice could accelerate.”

The resolution of Bedmap3 is unprecedented. The map is gridded at 500-meter intervals, whereas previous maps used 5-kilometer grids. This finer scale allows scientists to see features like subglacial mountains and valleys that were previously blurred or invisible.

One striking revision is the location of the thickest ice. Earlier maps identified the Astrolabe Basin in Adélie Land as the record holder. But Bedmap3 reveals that the true heavyweight lies in an unnamed canyon in Wilkes Land, where the ice reaches a staggering 4,757 meters thick — more than 15 times the height of the Shard, London’s tallest skyscraper.

The map also includes a new classification of Antarctica’s ice. In addition to distinguishing between grounded ice (which sits on land) and floating ice shelves, the team identified areas of “transient grounding,” where ice shelves temporarily touch the seabed during low tides. These zones, which can influence ice dynamics and ocean circulation, were previously overlooked.

What’s Next for Antarctica?

Antarctica’s ice sheet is thicker and more extensive than previously thought, with a larger volume of ice grounded on bedrock below sea level. This makes it more susceptible to melting as warm ocean water encroaches on the continent’s edges.

“What Bedmap3 is showing us is that we have got a slightly more vulnerable Antarctica than we previously thought,” said Peter Fretwell, a mapping specialist at BAS and co-author of the study.

The stakes are high. Satellite tracking shows that Antarctica lost 168 billion tonnes of ice in 2023 — the sixth highest year on record — owing to the continued speedup of glaciers in West Antarctica and record melting from the Antarctic Peninsula. Even a small fraction of its ice sheet could have devastating consequences for coastal communities worldwide were it to melt. From 2002 to 2017, melting ice sheets accounted for roughly a third of global sea level rise, according to the National Snow and Ice Data Center.

This is why this current effort is so important — and it’s far from over. Many areas of Antarctica remain poorly surveyed, particularly beneath its vast ice shelves. Future missions, equipped with more advanced technology, will continue to fill in the gaps.

The findings appeared in the journal Scientific Data.