Pace of Antarctic glacier collapsing into sea accelerates
The Pine Island ice shelf lost a fifth of its area between 2017 and 2020, and retreated by 19 kilometers (approximately 12 miles) during that time.
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I took the photo above about 2 am in the morning of December 26, 1965 as I followed an unsteady contingent of my shipmates back to our ship parked in the icy harbor at McMurdo Sound, Antarctica from a quonset hut optimistically repurposed as the Playboy Club at the research station there. All in all, it was not a bad place to be if you happened to be of draft age in 1965.
Alas, it may not be the safe harbor it was during my visit. A new research paper, published in Science Advances last week, found that the Pine Island Glacier, currently the frozen continent’s greatest contributor to sea level rise, could be closer to collapse than previously thought. The glacier had sped up by 12 percent over the last three years as the ice shelf holding it in place breaks up. This finding could accelerate the timeline for when the entire glacier collapses into the sea, and underscores the urgency of acting to combat the climate crisis.
For decades, the ice shelf has helped to hold back one of the fastest-moving glaciers in Antarctica. Analysis of satellite images reveals a more dramatic process in recent years: From 2017 to 2020, large icebergs at the ice shelf’s edge broke off, and the glacier sped up.
Since floating ice shelves help to hold back the larger grounded mass of the glacier, the recent speedup due to the weakening edge could shorten the timeline for Pine Island Glacier’s eventual collapse into the sea. Researchers at the University of Washington and British Antarctic Survey analyzed satellite images to show that the ice shelf lost a fifth of its area between 2017 and 2020, and retreated by 19 kilometers (approximately 12 miles) during that time. Lead author and University of Washington glaciologist Ian Joughin said in the press release:
“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected. 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.”
"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. "It's not at all inconceivable to say the rest of the ice shelf could be gone in a decade. It's a long shot. But it's not that big a long shot."
The Pine Island Glacier is one of two Antarctic glaciers that most concerns scientists. It and the Thwaites Glacier sit side-by-side in western Antarctica, and keep the rest of the region's ice in check.
Pine Island Glacier contains approximately 180 trillion tons of ice — equivalent to 0.5 meters, or 1.6 feet, of global sea level rise. It is already responsible for much of Antarctica’s contribution to sea-level rise, causing about one-sixth of a millimeter of sea level rise each year, or about two-thirds of an inch per century, a rate that’s expected to increase. If it and neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, global seas could rise by several feet over the next few centuries. The Pine Island Glacier on its own contains enough ice to bump sea levels up by 1.6 feet if it melted.
Pine Island’s shelf is important because it’s helping to hold back this relatively unstable West Antarctic glacier, the way the curved buttresses on Notre Dame cathedral hold up the cathedral’s mass. Once those buttresses are removed, the slow-moving glacier can flow more quickly downward to the ocean, contributing to rising seas.
Co-author Pierre Dutrieux, an ocean physicist at British Antarctic Survey, is concerned about the accelerated timetable.
“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. So it’s a potentially much more rapid and abrupt change.”
“Sediment records in front of and beneath the Pine Island ice shelf indicate that the glacier front has remained relatively stable over a few thousand years,” Dutrieux added. “Regular advance and break-ups happened at approximately the same location until 2017, and then successively worsened each year until 2020.”
The images, recorded by the European Space Agency's Copernicus Sentinel-1 satellites, were taken every 12 days between 2015 and 2017, and every six days between 2017 and the present. The study also looked at the relationship between the breakup of the ice shelf and the retreat of the glacier, and found that the glacier's movements were directly related to the ice 's deterioration.
The study from researchers at the University of Washington and British Antarctic Survey was funded by the U.S. National Science Foundation, NASA and the U.K. Natural Environment Research Council. Other co-authors are Daniel Shapero and Ben Smith at the UW; and Mark Barham at British Antarctic Survey.
Dig Deeper
Ice-shelf retreat drives recent Pine Island Glacier speedup
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