Fast-losing Antarctic glacier has lost ice even faster in the past, raising concerns for the future
West Antarctica’s Thwaites Glacier, the size of Florida, is the elephant in the room for scientists trying to make global sea-level predictions. The massive ice flow is rapidly retreating – effectively collapsing when viewed on geologic timescales. This has led to widespread concern about how quickly it can give up its ice to the ocean. The potential impact is dire: The complete loss of Thwaites and the surrounding ice basins could raise sea levels by 3 to 10 feet. Now, a a new study of Art Natural science adds cause for concern.
In the course of the study, scientists for the first time mapped a critical section of the seabed in front of the glacier in high resolution. The team documented more than 160 parallel ridges that were created like tracks as the front edge of the glacier receded and bobbed up and down with daily tides over the past 200 years. Alarmingly, the rate of retreat indicated by the ridges is much higher than what scientists have documented more recently.
To understand Thwaites’ past retreat, the team analyzed reef formations submerged 700 meters (just under half a mile) beneath the polar ocean and accounted for the region’s tidal cycle as predicted by computer models. This showed that one rib had to form every day. At one point, in less than six months, the front of the glacier lost contact with the seafloor ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles)—double the rate recorded by satellites since 2011 until 2019. .
U.S. research vessel Nathaniel B. Palmer, photographed by drone at the Thwaites Ice Front, February 2019. (Alexandra Mazur/University of Gothenburg)
“It’s like you’re looking at a tide on the sea floor,” said lead author Alistair Graham of the University of South Florida. “Our results show that pulses of very rapid retreat have occurred on Thwaites Glacier over the past two centuries and possibly as recently as the mid-20thousand century,” he said.
“Thwaites is really holding on by its fingernails today, and we should expect big changes in the short term in the future,” said study co-author Robert Larter of the British Antarctic Survey.
The research team included Frank Nietzsche Columbia Climate School Lamont-Doherty Earth Observatoryalong with other scientists from the USA, Great Britain and Sweden.
To collect images and supporting geophysical data, scientists launched a robot with sensors from a US icebreaker Nathaniel B. Palmer in Expedition 2019, the robot embarked on a 20-hour mission that was as risky as it was random. He mapped the area of ​​the seafloor in front of a glacier roughly the size of Houston during a sea-ice-free summer, allowing scientists to access the glacier’s front for the first time in history. Scientists describe the expedition itself in the accompanying paper.
A 3D rendering of a seafloor figure in depth color collected just in front of the Thwaites Ice Shelf. (Alastair Graham/University of South Florida)
Graham said the team would like to directly sample seafloor sediments so they can date the ridge-like features more precisely. “The ice closed us in pretty quickly and we had to leave before we could do that,” he said.
Scientists used to think that Antarctic ice sheets were slow to respond to climate conditions, but that’s no longer the case, Graham said. “Just a small nudge to Thwaites can lead to a big response,” he said.
The study is part of a long-term international cooperation to study Thwaites and inform global sea-level rise planning efforts. According to the United Nations, approximately 40 percent of the population lives within 60 miles of the coast.
The research was supported by the US National Science Foundation and the UK’s Natural Environment Research Council.
Adapted from a University of South Florida press release.
