According to a study, the Thwaites Glacier, known as the "doomsday glacier" for its risk to global sea levels, is receding faster than previously thought.
At approximately 120 km wide, Thwaites is the largest glacier on Earth and is one of Antarctica’s most fragile glaciers. According to high-resolution images taken on the seafloor, the Glacier in West Antarctica has been retreating for some time. Scientists’ findings suggest the massive piece of ice may have retreated even faster in the past than it does now, raising concerns about its future.
For scientists trying to predict global sea level rise, the Thwaites Glacier in West Antarctica has been an elephant in the room. It is truly massive and can be compared in size to the United Kingdom or the state of Florida.
As the massive ice shelf retreats rapidly (called a collapse on geological timescales), the amount or speed at which it may lose its ice to the ocean has raised widespread concern. Sea levels could rise by up to 65 cms due to Thwaites’ retreat.
This is the first time a high-resolution map has been created of a critical part of the seafloor in front of the glacier, giving scientists a better understanding of how fast Thwaites has retreated in the past. In addition, geologic features that were previously unknown to science are revealed in the stunning imagery, which also provides a glimpse at what Thwaites’ future holds.
More than 160 parallel ridges were created by the glacier’s leading edge reversing and bobbling with the tides, leaving a footprint.
Dr. Ali Graham, the lead author and professor at Florida University says the image looks like a tide gauge on the seafloor. “It really blows my mind how beautiful the data are.”
However, Graham noted that, despite the beauty, the rate at which Thwaites was retreating more recently is very slow compared to how quickly it changed in the past.
Researchers analyzed rib-like formations deep beneath the polar ocean to learn about Thwaites’ past retreat. In accordance with computer models, the tidal cycles in the region must have created one ‘rib’ every single day.
Over a period of fewer than six months in the last 200 years, the glacier front lost contact with the seabed ridge and receded at a rate of 2.1 kilometers per year (1.3 miles per year), twice as fast as satellite data between 2011 and 2019.
The findings suggest that Thwaites Glacier has undergone pulses of rapid retreat in the last two centuries and possibly as recently as the mid-20th century.
British Antarctic Survey researcher and co-author Dr. Robert Larter says, “The Thwaites glacier is holding on by its fingernails right now, and we should expect big changes over short timescales in the future – even within the next year – once the glacier recedes beyond a shallow ridge in its bed.”
The team, consisting of a research group from the United States, the United Kingdom, and Sweden, launched an orange robotic vehicle called Rán, equipped with imaging sensors, during an expedition in 2019 from the R/V Nathaniel B. Palmer in order to obtain the imagery and supporting geophysical data.
Rán was operated by scientists from the University of Gothenburg in Sweden on a mission that was both risky and serendipitous, Graham said. During an unusual summer without sea ice, the team mapped a seabed area around the size of Houston in front of the glacier, allowing access to the glacier’s front for the first time.
Ann Wahlin, a physicist at the University of Gothenburg who deployed Rán at Thwaites, describes it as a pioneering ocean floor study enabled by technological advancements in autonomous ocean mapping and the Wallenberg Foundation’s bold investment in this research infrastructure. The images Rán collected provide the researchers with valuable insights into what is happening at the critical intersection of glaciers and oceans today.
It was a once-in-a-lifetime mission,” said Graham, who added that the team is interested in sampling the seabed sediments directly so that they can date the ridge-like features more accurately. “But the ice closed in on us pretty quickly, and we had to leave before we could do that on this expedition,” he said.
There are still many questions to be answered, but one thing’s for sure: scientists once thought the Antarctic ice sheets were slow and sluggish to respond, but that’s simply not true, Graham said. “Just a small kick to Thwaites could lead to a big response,” he said.
According to the United Nations, approximately forty percent of the global population lives within 60 miles of the coast. Tom Frazer, dean of the College of Marine Science, University of South Florida, said, “Thwaites is out of sight, but it can’t be overlooked.” This study is part of a cross-disciplinary effort to understand how the glacier system works. As part of our efforts to inform global planning efforts, this study is an important step forward.
The results of the research were published in the journal Nature Geoscience.
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