The underside of glaciers remains a mystery, but now the first detailed maps made by an unmanned submersible in West Antarctica have revealed clues about future sea level rise.
The Ran autonomous underwater vehicle has been submerged in the cavity of the Dotson Ice Shelf in West Antarctica to scan the ice above it with an advanced sonar system. Over 27 days in 2022, it travelled more than 1,000 kilometres round trip, reaching 17 kilometres deep into the cavity.
The results of their journey are published in a study led by the University of Gothenburg (Sweden) that documents never-before-seen shapes at the bottom of an Antarctic ice shelf, shaped by the circulation of warm water.
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A shelf is a mass of glacial ice fed from land by tributary glaciers, which floats at sea above an ice shelf cavity.
Normally, satellite data and ice cores are used to observe glacier change, but the submersible was able to obtain high-resolution maps of the underside of the ice. “It’s a bit like seeing the far side of the Moon,” said lead author Anna Wåhlin from the University of Gothenburg.
The new data and images “may provide key missing information to improve model projections of ice shelf melt and sea level rise,” as well as opening a new avenue of scientific research, according to the study published in Science Advances.
Future sea level rise
The Dotson Ice Shelf is adjacent to the Thwaites Glacier, which is thought to have a major impact on future sea level rise due to its size and location.
The glacier is melting fastest where strong underwater currents erode its base, and scientists were able to measure currents beneath the glacier for the first time to show why the western part of the Dotson Ice Shelf is melting so fast.
They also observed signs of very high melting in the vertical fractures that extend across the glacier.
The rover also recorded data on salinity, temperature and water currents beneath the ice shelf, indicating that previously unquantified basal melting mechanisms occur beneath the shelf and probably beneath other ice shelves.
Forms unknown until now
High-resolution maps revealed previously unknown features at the base of the ice shelf, with inverted grooves ranging from 20 to 300 metres in length that only appeared at the western base of the ice shelf, which is experiencing the highest rates of basal melting.
“I couldn’t stop looking at it,” Wåhlin told The New York Times. “We had no idea it could look like this.”
These unknown shapes create ice peaks and valleys with plateaus and formations resembling sand dunes. Researchers hypothesize that these could have been formed by the flow of water under the influence of the Earth’s rotation.
The team returned to Dotson’s platform this year with the Ran rover to repeat the studies, hoping to document the changes. The autonomous submarine was only able to make one dive before disappearing beneath the ice without a trace.
“While we recovered valuable data, we did not get everything we had hoped for. These scientific breakthroughs were made possible by the unique submersible that was Ran. This research is necessary to understand the future of the Antarctic ice sheet and we look forward to taking over from Ran and continuing this important work,” Wåhlin said.
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