An unexpected and previously unknown topography beneath Antarctica's floating ice shelves has come to light, courtesy of a new study. When a team of international scientists examined the underside of the Dotson Ice Shelf, they were astounded to find an upside-down landscape, featuring peaks, valleys and plateaus.
Anna Wahlin, a professor of physical oceanography at the University of Gothenburg in Sweden, who led the research team, told the BBC, "We were surprised - we had to double check it was real," adding, "There is a landscape of ice down there we had no idea about before."
In 2022, Wahlin's team used an unmanned submersible to explore the underside of the Dotson Ice Shelf, located in West Antarctica. The submersible travelled over 1,000 kilometres under 350 metres of ice, providing the first-ever map of the ice shelf's underside. The data collected during the 27-day mission revealed an intricate ice-scape.
The discovery is crucial to understanding how melting ice could influence global sea levels. The West Antarctic Ice Sheet (WAIS), which is experiencing rapid ice loss, is a major contributor to rising sea levels. Wahlin said the WAIS is "a massive amount of ice - it would be dramatic if it were to end up in the ocean." Scientists have long observed the melting of WAIS through satellite imaging, but the exact rate of this melting remains uncertain.
As world leaders discussed sea level rise at COP29, these researchers studied ice shelf melt to better predict its impact on coastal cities. Thwaites Glacier, one of the largest glaciers in WAIS, is of particular concern. If it were to completely melt, it could raise global sea levels by as much as 65 cm. "Over the last 30 years Thwaites' (melt rate) has pretty much doubled - and we know that's accelerating. We think it's going to keep accelerating, and at some point, it could get much quicker," said Alex Brisbourne, a glacier geophysicist at the British Antarctic Survey (BAS).
While ice shelf melt doesn't directly raise sea levels, it accelerates ice loss by allowing glaciers to flow into the ocean. The rapidly thinning Dotson Ice Shelf's interactions with seawater are key to predicting future melting patterns. Experts emphasise the importance of understanding seawater circulation near the shelf to grasp how ocean temperature changes drive ice melt.
The team's unmanned submersible 'Ran' was programmed with hundreds of commands to explore the ice shelf, and though the researchers were nervous as it sank out of sight, they were amazed when it returned with detailed images showing peaks, valleys, plateaus and teardrop-shaped formations beneath the ice.
"It looked like the Grand Canyon. There were plateaus and swirly patterns melted into the ice," Wahlin said. One of the most surprising discoveries were the "scoops" of ice. "It was as if a giant had taken an ice cream scoop and scooped it out," Wahlin added. The team counted 75 of these formations, some stretching over 300 metres and reaching depths of up to 20 metres.
The study of ice shelf melt has broader implications for global ecosystems, as the region surrounding the Dotson Ice Shelf is a biological hotspot. Patricia Yager, an oceanographer, who studied the impacts of climate change on marine ecosystems in Antarctica, said, "It's so far away. It takes forever to get there (to Antarctica). But it's hugely touched." She noted that the increasing volume of meltwater entering the ocean is changing the salinity of the water and disrupting the formation of seasonal sea ice, which could have significant consequences for the region's food webs.
In 2024, Wahlin's team returned to Antarctica to continue their research, but after two dives, 'Ran' disappeared without a trace. "We did notice many Weddell seals in the area," Wahlin said, suggesting the seals may have interfered with the submersible's movements, causing it to become stuck and shut down to conserve energy. Still, Wahlin hopes to continue the work, saying, "We hope to be able to replace Ran and continue this important work. I would love to go back and look again at the patterns - to see how they change over the years."
