Scientists have used an unmanned submarine for the first time to map the underwater terrain near a massively melting glacier in West Antarctica, showing it has the potential to retreat at twice the rate observed by satellites during the last decade
Key points:
- The Thwaites Glacier is nicknamed the “doomsday glacier” because of its potential to cause a rapid rise in sea level if it were to melt.
- Antarctic researchers have found that it melted at twice the rate previously thought possible sometime in the past 200 years.
- One of the researchers says the glacier is “holding on by its fingernails” and we could see rapid melting in the future
Thwaites Glacier, named after glacial geologist Fredrik Turville Thwaites, is known as the “doomsday glacier” in scientific circles for its potential to significantly raise global sea levels, as well as its vulnerability to rapid melting due to warming ocean water.
A team of researchers from the United States, the United Kingdom, and Sweden traveled to Antarctica on the icebreaker research vessel Nathaniel B. Palmer in early 2019 to map an ancient land area of the glacier, the area where a shelf of ice gradually joined solid ground. transitions to a floating ice platform.
Researchers hoped that by studying the past retreat of Thwaites Glacier, they could gain a new understanding of what it has the potential to do in the future, amid speculation that it could be a potential candidate for climate engineering projects to prevent a collapse
They used a bright orange autonomous underwater vehicle (UAV) called the Rán, mounted with two types of geophysical sensors, to produce 3D scans of the underwater surface.
The 19-hour mission produced about 13 square kilometers of new geophysical data, collected from between 50 and 90 meters above the sea floor.
The Rán autonomous underwater vehicle floats through the sea ice in front of the Thwaites Glacier after a nearly 20-hour mission to map the seabed. (University of Gothenburg: Anna Wåhlin)
By analyzing the width and spacing of the ridges left by the glacier on a raised part of the seafloor—an isolated submarine outcrop they called “the bump” at the southwest corner of the tongue of the glacier—, they were able to determine that the marks, or “ribs,” had been left by the glacier rising and settling with the ocean’s tide each day.
They found that Thwaites Glacier was susceptible to rapid retreat, shrinking at a rate of more than 2.1 kilometers per year when the marks were left.
That’s double the rate of retreat observed by satellite between 2011 and 2019, which was previously thought to be the upper limit of the glacier’s potential shrinking rate.
Multibeam bathymetry images captured by Rán show “ribs” and melt channels in underwater terrain near Thwaites Glacier. (Nature Geoscience)
Dr. Alastair Graham of the University of Florida, who led the Antarctic mission and was co-senior author of a study published Monday in Nature Geoscience, said the glacial retreat documented by the team would have occurred in sometime in the last two centuries, possibly as recently as the mid-1900s.
While he called the opportunity to map the area “a truly once-in-a-lifetime mission,” he was at pains to point out that what they had found shattered his earlier hope that the Antarctic ice sheets could be slow and slow to respond. to climate changes.
“Just a small kick in Thwaites could trigger a big response,” Dr Graham said.
R/V Nathaniel B. Palmer at the Thwaites Glacier ice front in 2019. (University of Gothenburg: Alexandra Mazur)
Dr Graham added that his team had wanted to sample the seabed directly so they could date the ‘bump’ marks more precisely, but “the ice closed in very quickly and we had to leave before we could it in this expedition.”.
Dr. Robert Larter, a marine geophysicist and co-author of the study, said that once the glacier retreats beyond a shallow ridge in its bed, it has the potential to shrink at an even greater rate.
“Thwaites is really holding on today, and we should expect to see big changes on small time scales going forward, even from year to year,” he said.
A study led by NASA in 2019 discovered a gigantic cavity under the glacier that is estimated to have once contained 14 billion tons of ice. The researchers believe that most of this ice would have melted over the previous three years.