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In 2022, an international team of scientists sent a 20-foot-long autonomous underwater vehicle (AUV) named “Ran” to traverse the never-explored region beneath the Dotson Ice Shelf in West Antarctica.
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The resulting study revealed the complicated dynamics that are leading to the faster melting rates between the ice shelf’s western and eastern portions.
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After returning to the area in 2024 to catalog changes to the ice shelf, “Ran” became lost beneath the icy waves—a huge setback for the exploration of this critically important, climate change-stressed area.
When figuring out a solution, it helps to approach a problem from every possible angle. The same can be said for climate change-induced ice melt in the Antarctic, which is why the International Thwaites Glacier Collaboration (ITGC) programmed an automated underwater vehicle (AUV)—nicknamed “Ran”—to dive into the cavity of the Dotson Ice Shelf, located near Thwaites Glacier in West Antarctica.
Over the course of 27 days, the submarine traveled more than 600 miles—including 10 miles directly into the cavity itself—to both figure out the mechanics of how glaciers melt faster near strong underwater currents and glimpse the topography of this all-important ice shelf. What the experts behind this submersible found is that the attributes along the western part of the ice shelf differ greatly with the eastern portion, which is thicker and therefore melting more slowly.
The Ran AUV also produced high resolution maps of the underside of the Dotson Ice Shelf that revealed strange tear-drop features, icy plateaus, and detailed erosion patterns. The results of the study were published last week in the journal Science Advances.
“We have previously used satellite data and ice cores to observe how glaciers change over time,” Anna Wåhlin, the lead author of the study, said in a press statement. “By navigating the submersible into the cavity, we were able to get high resolution maps of the ice underside. It’s a bit like seeing the back of the Moon.”
Unlike glaciers, which rest on land, ice shelves are actually a part of the ocean. They sort of act like a buttress that keeps ice on land from flowing into the ocean and raising sea levels, and are are vitally important to these polar ecosystem as a result. And because these shelves rest on the ocean, it’s possible to get under them.
But just because it’s possible doesn’t mean it’s easy.
The 20-foot-long Ran submersible used pulsed sound waves (advanced multibeam sonar) on the ice to map its features, but because of its subantarctic location, Wåhlin and her team couldn’t communicate with the AUV or track its movements with GPS. After 14 missions—some lasting a couple hours and others stretching longer than a day—Ran mapped around 50 square miles of ice, and the structures imaged were more complex than anyone imagined.
“The mapping has given us a lot of new data that we need to look at more closely,” Wåhlin said in a press statement. “It is clear that many previous assumptions about melting of glacier undersides are falling short. Current models cannot explain the complex patterns we see. But with this method, we have a better chance of finding the answers.”
One of the team’s discoveries is that the different melt rates between east and west portions of the Dotson Ice Shelf could be explained by a phenomenon known as the modified Circumpolar Deep Water (mCDW), which is when Pacific and Indian Ocean water mix with other local water masses that impact the ice base. This data was supplemented by Ran’s measurements of these underwater currents, as well as the high melting rates of fractures that run through the glacier.
Although the team’s initial mission was to study the nearby Thwaites glacier, the environment proved too difficult to access. The Dotson Ice Shelf, however, served as the perfect candidate to test the equipment and methods, according to The New York Times. These surveys were conducted in 2022, and the team returned earlier this year to see what changes to the ice shelf had occurred. That’s when Wåhlin and her team’s worst fears were realized—Ran didn’t emerge at the pre-planned rendezvous point. The team suspects that the AUV either ran aground or became the target of some curious seals.
“Although we got valuable data back, we did not get all we had hoped for. These scientific advances were made possible thanks to the unique submersible that Ran was,” Wåhlin said in a press statement. “This research is needed to understand the future of Antarctica’s ice sheet, and we hope to be able to replace Ran and continue this important work.”
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