Ice shelf disintegration accelerating Pine Island Glacier descent toward sea

Already Antarctica's fastest moving glacier, new research suggests Pine Island Glacier's descent into the sea is accelerating as its ices shelf weakens.

Scientists at the University of Washington and British Antarctic Survey detailed Pine Island's worrying prognosis in a new paper, published Friday in the journal Science Advances.

"We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected," study lead author Ian Joughin said in a press release.

"The processes we'd been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf," said Joughin, a glaciologist at Washington's Applied Physics Laboratory.

Several recent studies have highlighted the myriad threats -- rising air and water temperatures, encroaching warm water currents, declining snowfall -- facing Pine Island Glacier and much of the ice shelf that lines the coast of the Antarctic Peninsula.

Much of the recent research emphasized the threat posed by warm water currents. Between 2000 and 2009, Pine Island Glacier and neighboring Thwaites Glacier rapidly thinned, allowing warm water currents to penetrate further inland, accelerating melt rates.

Over the last decade, however, both Pine Island and Thwaites glaciers slowed their descent toward the Amundsen Sea, appearing to stabilize -- at least until recently.

The latest study, which relied on recent satellite images captured between 2017 and 2020, suggests Pine Island Glacier is deteriorating in a new way, losing large chunks of ice all at once.

Since 2017, Pine Island Glacier's ice shelf has lost one fifth of its surface area to iceberg calving. The latest analysis suggests internal stress, not warm water, is to blame.

"The ice shelf appears to be ripping itself apart due to the glacier's acceleration in the past decade or two," Joughin said.

Using the satellite images collected by the European Space Agency's Copernicus Sentinel-1 satellites, researchers tracked the movement of two inland locations on Pine Island's surface between 2017 and 2020.

The data showed the glacier's flow accelerated by 12 percent.

"The recent changes in speed are not due to melt-driven thinning; instead they're due to the loss of the outer part of the ice shelf," Joughin said. "The glacier's speedup is not catastrophic at this point. But if the rest of that ice shelf breaks up and goes away then this glacier could speed up quite a lot."

Pine Island and Thwaites are just two of several coastal glaciers acting as a dam holding back the descent of the West Antarctic Ice Sheet into the Southern Ocean.

Currently, the ice sheet is responsible for just 10 percent of global sea level rise, but that number would surely increase -- and rapidly -- if Pine Island or one of its neighbors collapse.

Though scientists aren't yet sure whether Pine Island's ice shelf will continue to disintegrate as it has over the few years, the latest research suggests the imperiled glacier is much closer to its eventual collapse than scientists realized.

"The loss of Pine Island's ice shelf now looks like it possibly could occur in the next decade or two, as opposed to the melt-driven subsurface change playing out over 100 or more years," study co-author Pierre Dutrieux said in the release.

"So it's a potentially much more rapid and abrupt change," said Dutrieux, an ocean physicist at British Antarctic Survey.

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