R/V Nathaniel B. Palmer image from a drone at Thwaites Glacier in February 2019. Credit: Alexandra Mazur/University of Gothenburg
Faster in the past: New seafloor images – the highest resolution of any image taken of the West Antarctic ice sheet – have upended understanding of the Thwaites Glacier Retreat.
At times in the past, the huge Thwaites glacier retreated faster than it is today, raising concerns about its future.
The Thwaites Glacier in West Antarctica, also known as the Doomsday Glacier, has been an elephant in the room for scientists trying to predict global sea level rise.
This massive glacier stream is already in a phase of rapid retreat (“breakdown” when viewed on geological time scales). This has led to widespread concern about how much or how quickly it might give up its ice into the ocean.
3D view of multi-beam bathymetry (seafloor shape) color by depth, collected by Rán across a ridge on the sea floor, just in front of the Thwaites ice shelf. Credit: Alistair Graham/University of South Florida
The potential effect of Thwaites’ retreat is backbone cooling: Loss of the glacier and the surrounding ice basins could raise sea levels by three to 10 feet. The glacier is the size of Florida.
“Thwaites is really sticking with its nails today, and we should expect to see big changes on small time scales in the future – even from year to year – once the glacier retreats beyond a shallow ridge at its bottom.” – Robert Larter
A new study was published in
“It’s like you’re looking at a tide gauge on the sea floor,” Graham said. “It really amazes me how beautiful the data is.”
Aside from the beauty, Graham said, what is worrisome is that the rate of decline of Thwaites that scientists have documented recently is tiny compared to the fastest rates of change in the past.
To understand Thwaites’ previous retreat, scientists analyzed submerged rib-like formations 700 meters (about 2,300 feet or just under half a mile) below the Arctic Ocean and factored in the region’s tidal cycle and, as computer models predicted, showed that one rib must be It has been configured every day.
Rán, an autonomous Kongsberg HUGIN underwater vehicle, is among the sea ice in front of the Thwaites Glacier, after a 20-hour mission to map the sea floor. Image Credit: Anna Wåhlin / University of Gothenburg
At some point in the past 200 years, over a period of less than six months, the glacier front lost contact with the edge of the sea floor and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year). This is double the rate documented using satellites between 2011 and 2019.
“Our results suggest pulses of very rapid retreat occurred in the Thwaites glacier in the past two centuries, and possibly as recently as the mid-20th century,” Graham said.
“Thwaites is really sticking with its nails today, and we should expect to see big changes on small time scales in the future – even from year to year – once the glacier retreats beyond a shallow rim at its bottom,” said the marine geophysicist. And co-author Robert Larter of the British Antarctic Survey.
Thwaites Glacier map shown in Landsat 8 satellite imagery collected in February 2019. The path of the Autonomous Underwater Vehicle mission is shown in orange. Changes in the positions of the Thwaites Glacier’s grounding line in the recent past are shown by colored lines. Credit: Alistair Graham/University of South Florida
To collect images and supporting geophysical data, the research team, which included scientists from the US, UK and Sweden, launched a modern orange robotic vehicle loaded with imaging sensors called ‘Rán’ from R/V Nathaniel B. Palmer during an expedition in 2019.
Graham said Rán, run by scientists at the University of Gothenburg in Sweden, embarked on a 20-hour mission that was as risky as it was serendipitous. It mapped a sea floor roughly the size of Houston in front of the glacier—and did so in harsh conditions during an unusual summer marked by its lack of sea ice.
This allowed researchers to reach the glacier front for the first time in history.
“This was a ground-breaking study of the ocean floor, made possible by recent technological advances in autonomous ocean mapping and the Wallenberg Foundation’s bold decision to invest in this research infrastructure,” said Anna Wahleen, a physical oceanographer from the University of Gothenburg. Ran Publishing in Thwaites. “The images Ran collected give us vital insights into the processes that occur at the critical junction between the glacier and the ocean today.”
“It was really a once-in-a-lifetime task,” Graham said, who said the team would like to sample directly from the seafloor sediments so they can more accurately date hill-like features.
“But the ice closed in on us very quickly and we had to leave before we could do that on this expedition,” he said.
Thor scientists Alistair Graham (right) and Robert Larter (left) look in awe at the rickety, icy face of Thwaites’ Ice Rim, from the bridge deck in R/V Nathaniel B. Palmer. Credit: Frank Nietzsche
While many questions remain, one thing is certain: Scientists used to think that Antarctic ice sheets were slow and slow to respond, but that’s simply not true, according to Graham.
“Just a small kick for Thwaites can lead to a big response,” he said.
According to the United Nations, nearly 40 percent of the population lives within 60 miles of the coast.
Tom Fraser, dean of the USF School of Marine Sciences, said, “This study is part of an interdisciplinary team effort to better understand the Thwaites Glacier system, and because out of sight, we can’t get Thwaites out of mind. This study is an important step forward in providing key information To enlighten global planning efforts.”
Reference: “The Rapid Retreat of Thwaites Glacier in the Pre-Satellite Era” by Alistair JC Graham, Anna Wolin, Kelly A. Hogan, Frank O. Nechi, Karen J. Heywood, Rebecca L. Totten, and James A. Dieter Hillenbrand, Lauren M. Simkins, John B. Anderson, Julia S. Wellner, Robert D. Larter, 5 Sep 2022, Available here. natural earth sciences.
DOI: 10.1038 / s41561-022-01019-9
The study was supported by the National Science Foundation and the UK Natural Environment Research Council through the Thwaites Glacier International Collaboration.
The 2019 expedition was the first in a five-year project called THOR, which stands for Thwaites Offshore Research, and also included team members from a sister project called Thwaites-Amundsen Regional Survey and Network Integration Atmosphere-Ice-Ocean Processes, or TARSAN.