October 6, 2022

Antarctica’s rapidly receding glaciers have lost ice faster in the past, raising concerns for the future.

Antarctica’s rapidly receding glaciers have lost ice faster in the past, raising concerns for the future.

West Antarctica’s Thwaites Glacier, about the size of Florida, is the elephant in the room for scientists trying to predict global sea levels. The massive ice stream is retreating rapidly – ​​in fact in a state of collapse, when seen on geologic time scales. This has led to widespread concern about how fast it might give up its ice to the ocean. The potential impact is dire: the total loss of Thwaites and its surrounding ice basins could raise sea levels by 3 to 10 feet. Now, A A new study in Nature Earth Sciences It causes concern.

In this study, for the first time, scientists mapped a critical zone of seabed in front of the glacier in high resolution. The team recorded more than 160 parallel ridges that, like footprints, were created when the leading edge of the glacier retreated and moved up and down with daily tides sometime over the past 200 years. Alarmingly, the rate of retreat indicated by the ridges is much faster than scientists have recently recorded.

To understand Thwaites’ past retreat, the team analyzed rib-like structures located 700 meters (just under half a mile) below the Arctic Ocean and analyzed the tidal cycle for the region, as predicted by computer models. It was possible, they got an invoice. This indicated that a rib had to be formed every day. In a time period of less than six months, the glacier front was cut off by the seafloor ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles)—twice the rate recorded using satellites between 2011 and 2019.

American research vessel Nathaniel B. Palmerphotographed from a drone on the Thwaites Ice Front, February 2019. (Alexandra Mazur/University of Gutenberg)

“It’s like you’re looking at a tide on the sea floor,” said lead author Alastair Graham of the University of South Florida. “Our results show that pulses of very rapid retreat have occurred in Thwaites Glacier over the past two centuries and possibly into the mid-20th century,” he said.

Robert Larter of the British Antarctic Survey says: “The Thwaites really hold today by their fingernails and we should expect big changes on small timescales in the future.”

The research team included Frank Nietzsche from the Columbia School of Climate Lamont-Doherty Earth Observatoryalong with other scientists from the United States, Great Britain and Sweden.

To collect images and support geophysical data, scientists launched a robot carrying sensors from the American icebreaker. Nathaniel B. Palmer During a 2019 expedition, the robot embarked on a 20-hour mission that was just as dangerous. During a summer notable for lack of sea ice, it mapped an area of ​​seafloor in front of a glacier the size of Houston, giving scientists access to the glacier front for the first time in history. This journey itself has been described by scientists In an accompanying paper.

A 3D view of the sea floor with depth coloring collected just in front of the Thwaites Ice Shelf. (Alastair Graham/University of South Florida)

Graham said the team would like to directly sample the seafloor sediments so they can more accurately determine the stack-like features. “The ice closed in on us very 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 jab at Thwaites can lead to a big reaction,” he said.

Studying is part of A Long-term international cooperation For the Thwaites study, and to inform global efforts to plan for sea level rise. According to the United Nations, approximately 40 percent of the human population lives within 60 miles of the coast.

This study was supported by the US National Science Foundation and the UK Natural Environment Research Council.

Adapted from a University of South Florida press release.

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