Faster in the past: New undersea images — highest resolution ever taken from the West Antarctic ice sheet — upend understanding of Thwaites Glacier’s retreat.
At times, the giant Thwaites Glacier is retreating faster than it is now, fueling concerns about its future.
Thwaites Glacier in West Antarctica, also known as the Doomsday Glacier, has been the elephant in the room for scientists trying to make predictions of global sea level rise.
This massive ice stream is already in a phase of rapid retreat (“collapse” on a geological time scale). This has raised widespread concern about just how much or how quickly it might give up its ice to the ocean.
The potential impact of the Thwaites retreat is eerie: The complete disappearance of the glacier and surrounding icy basin could raise sea levels from 3 feet to 10 feet. The glacier is about the size of Florida.
“Thwaites really stick around on its nails today, and we should expect to see big changes on small timescales in the future – even from one year to the next – once the glacier retreats into a shallow ridge in its bed. outside.” — Robert Larter
A new study published in
“It’s like you’re looking at a tide gauge on the ocean floor,” Graham said. “The beauty of the data really blew me away.”
Aside from the beauty, the worrying thing is that the rate of Thwaites retreat recently recorded by scientists is small compared to the fastest rate of change in the past, Graham said.
To understand Thwaites’ past retreat, scientists analyzed ribbed formations submerged 700 meters (about 2,300 feet or less than half a mile) below the polar ocean, factoring in tidal cycles in the region, as predicted by computer models , indicating that a rib must be formed every day.
At some point in the past 200 years, in less than six months, the glacier front lost contact with the seafloor ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year). That’s twice the rate recorded using satellites between 2011 and 2019.
“Our findings suggest that Thwaites Glacier has experienced a very rapid retreat pulse over the past two centuries, most recently possibly in the mid-20th century,” Graham said.
“Thwaites really stuck on its nails today and we should expect to see big changes on small timescales in the future – even from one year to the next – once the glacier retreats into the shallow ridges on its bed. outside,” said marine geophysicist and study co-author Robert Larter from the British Antarctic Survey.
To collect the imagery and support geophysical data, a research team of scientists from the US, UK and Sweden from R/V Nathaniel B. Palmer on a 2019 expedition.
Rán, operated by scientists at the University of Gothenburg in Sweden, embarked on a 20-hour mission that was both risky and unexpected, Graham said. It mapped an area of the seabed about the size of Houston in front of the glacier, and it mapped the extreme conditions of an unusual summer marked by a lack of sea ice.
This allows researchers to access the glacier front for the first time in history.
Anna Wåhlin, a physical oceanographer at the University of Gothenburg, said: “This is groundbreaking research on the seafloor, thanks to recent technological advances in autonomous ocean mapping and the Wallenberg Foundation’s bold decision to invest in this research infrastructure.” Deploy Rán in Thwaites. “The images collected by Ran give us insight into the processes taking place at the critical interface between glaciers and oceans today.”
“It’s really been a once-in-a-lifetime mission,” said Graham, who said the team wanted to directly sample sediments on the seafloor so they could more accurately identify ridge-like features.
“But the ice came so close to us that we had to leave before we could do that on this expedition,” he said.
While many questions remain, one thing is certain: In the past, scientists thought the Antarctic ice sheet was sluggish and sluggish, but Graham believes that’s simply not true.
“A little kick on Thwaites could have a big repercussion,” he said.
About 40 percent of the population lives within 60 miles of the coast, according to the United Nations.
“This research is part of an interdisciplinary collective effort to better understand the Thwaites Glacier system,” said Tom Frazer, dean of the USF School of Marine Sciences, “and we can’t let Thwaites out of our minds just because it’s out of sight. This study is an important step forward in providing the necessary information for global planning efforts.”
Reference: “The Rapid Retreat of Thwaites Glacier in the Pre-Satellite Age” by Alastair GC Graham, Anna Wåhlin, Kelly A. Hogan, Frank O. Nitsche, Karen J. Heywood, Rebecca L. Totten, James A. Smith, Claus- Dieter Hillenbrand , Lauren M. Simkins, John B. Anderson, Julia S. Wellner, and Robert D. Larter, September 5, 2022, natural geosciences.
The research was supported by the US National Science Foundation and the UK’s Natural Environment Research Council through the International Thwaites Glacier Collaboration.
The 2019 expedition is the first of a five-year project called THOR, which represents Thwaites Offshore Research, and also includes input from a sister project called the Thwaites-Amundsen Regional Survey and Network Integrated Atmospheric-Ice-Ocean Processes or TARSAN. team member.