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Antarctic video reveals deepest canyon on Earth

SAN FRANCISCO, CALIFORNIA—Despite scientists’ best efforts to probe the land beneath Antarctica’s ice sheets with radar, the continent’s sheer size and remoteness has left many gaps in existing surveys. That changed this week with a new map, called BedMachine Antarctica, released at a meeting of the American Geophysical Union here and published yesterday in Nature Geoscience.

As shown in the video above, the map uses the flow and volume of ice to infer the land below. It has revealed the deepest canyon on Earth’s surface, plunging 3.5 kilometers below sea level under Denman Glacier in East Antarctica, nearly half as deep as Mount Everest is tall.

The uncovered terrain has mixed news for the future of Antarctica’s ice: On the positive side, the map reveals a series of previously unknown ridges that sit above sea level in the deep valleys that drain the Transantarctic Mountains, which helps stabilizes the glaciers above and limits their potential ice loss. But at West Antarctica’s fastest melting glacier, Thwaites, the news was not good: The glacier is grounded on a ridge below sea level, with a downward sloping basin behind it. The project hoped to turn up more ridges on the basin that could help hold back warm water as Thwaites retreats beyond the two already known. None was found.