Bild på undervattensfarkosten Ran
Underwater vehicle Ran brought back invaluable knowledge about Thwaites Glacier on her missions under the ice shelf.
Photo: Li Ling

AUV Ran brings answers to Doomsday Glacier history


Data from the Swedish underwater vehicle Ran show that the "Doomsday Glacier" has retreated much faster earlier in history compared to its current retreat. This is the first ever measurement made of the glacier's earlier movements, and the findings from Ran's underwater mission are now described by Anna Wåhlin from the University of Gothenburg, and her colleagues, in a study in Nature Geoscience.

The Thwaites Glacier in West Antarctica, also known as the "Doomsday Glacier”, has the potential to raise sea levels in the world’s oceans. The glacier has retreated several Swedish miles in the last 30 years according to satellite images, but has the melting been unusually fast compared to previous years? To try to answer that question, a group of researchers sent down University of Gothenburg’s autonomous underwater vehicle Ran beneath the glacier to take pictures of the sea floor.

Picture of Anna Wåhlin in front of AUV Ran
Polar researcher Anna Wåhlin in front of Ran, the University of Gothenburg’s underwater vehicle.
Photo: Olof Lönnehed

“It was extremely nerve-racking to send down Ran under the glacier. We could barely breathe during the day she was out on her mission. But she came back, and Ran's detailed measurements revealed clear marks of when the glacier retreated, about a hundred years ago. This was the first ever measurement made of the glacier's historical movements,” says Anna Wåhlin, polar researcher at the University of Gothenburg.

Precise tidal marks

Autonomous underwater vehicles such as Ran are very well suited for mapping and collecting data in ice-covered areas. They can go down and study areas below the ice, and even travel close to the sea floor, to provide close-up images of the tracks left by the glacier. Thwaites Glacier is monitored by satellites, but until now, scientists have had no data on changes in the Thwaites Glacier in historical time, before the satellite observations started.

A dataimage of the sea floor
Using the advanced equipment on Ran, the researchers could develop detailed images of the sea floor beneath Thwaites Glacier.

The measurements provided by Ran were so precise that the researchers could see even the small indentations in the sea floor created by each tidal wave against the glacier’s edge. And based on the marks on the sea floor, the researchers were able to calculate that the glacier at that time retreated approximately two kilometres per year, which is almost twice as fast as the current rate. This acquired knowledge is an important piece of the puzzle in the research on the glaciers in Antarctica.

“If we want to predict future rises of the sea level, we need to better understand the mechanisms that control the retreat of the glacier. Now, we have evidence that the glacier retreated much faster before, than it does today,” says Anna Wåhlin.

Blind spot on researchers' maps

The 2019 Polar Expedition brought together a large group of researchers from the USA, Great Britain, and Sweden. The main objective was to gather new knowledge to be able to predict the future of Thwaites Glacier, as the glacier has been a blind spot on the researchers' maps for a long time. During this expedition, the first measurements at the glacier's northern edge were carried out from the American icebreaker NB Palmer.

“Thanks to Sweden’s organisation for high-tech equipment, vessels, and technical specialists, we have the capacity to be a global leader in polar climate research. But we have to test and evaluate the equipment at home first, in order to succeed in these risky missions under the Antarctic ice. Our new research vessel Skagerak is a very valuable platform for preparing upcoming research missions. By testing and evaluating Ran and other underwater vehicles from Skagerak, we reduce severe risks in these polar missions.”

Many of Thwaites Glacier's fundamental characteristics are still unknown, such as its thickness, the depth of the sea floor beneath it, and the presence of, for example, underwater channels, ocean currents, and seamounts.

“Thwaite's Glacier is hanging on by a thread. We should expect big changes in the near future, sometimes even from one year to the next, says marine geophysicist Robert Larter, from the British Antarctic Survey.

Link to article: Rapid retreat of Thwaites Glacier in the pre-satellite era