SEATTLE, Wash. — One of Antarctica’s largest glacier’s is crumbling to pieces as it speeds towards total collapse within the next 20 years, a new study warns.
Researchers from the University of Washington say, for decades, Pine Island Glacier’s ice shelf has helped to hold back one of the fastest-moving glaciers in Antarctica. Unfortunately, that ice shelf is gradually thinning. Now, analysis of satellite images reveals a more dramatic melting process in recent years.
From 2017 to 2020, large icebergs at the ice shelf’s edge have broken off and the glacier is speeding up. Since floating ice shelves help to hold back the larger grounded mass of the glacier, study authors say that the recent acceleration due to the weakening edge could shorten the timeline for Pine Island Glacier’s eventual collapse into the sea.
“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 and glaciologist Professor Ian Joughin says in a university 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.”
Melting glaciers could lead to dramatic sea level changes
Pine Island Glacier contains around 180 trillion tons of ice, equivalent to roughly 1.6 feet of global sea level rise. Scientists say 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. That’s about two-thirds of an inch per century, a rate that researchers expect to increase.
If it and the neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, researchers say that global seas could rise by several feet over the next few centuries.
The glaciers’ ice shelves have thinned in recent decades because warmer ocean currents are melting the ice’s underside. From the 1990s to 2009, Pine Island Glacier’s motion toward the sea accelerated from 1.5 miles per year to 2.5 miles per year. The glacier’s speed then stabilized for almost a decade.
Prof. Joughin believes the results show that what’s happening now is a different process related to internal forces on the glacier. From 2017 to 2020, Pine Island’s ice shelf lost a fifth of its area in a few dramatic breaks monitored by satellites from the European Space Agency. The researchers analyzed images from January 2015 to March 2020 and discovered that the recent changes on the ice shelf are not directly related to ocean melting.
“The ice shelf appears to be ripping itself apart due to the glacier’s acceleration in the past decade or two,” Prof. Joughin explains.
Comparing glaciers to a collapsing building
Two points on the glacier’s surface scientists analyzed have sped up by 12 percent over the last four years. The research team used an ice flow model to confirm that the loss of the ice shelf caused the observed speed-up.
“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 continues. “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.”
Study authors add it’s not clear whether the shelf will continue to crumble as other factors, such as the slope of the land below the glacier’s receding edge, will come into play. However, they note the results change the timeline for when Pine Island’s ice shelf might disappear and how fast the glacier might move, boosting its contribution to rising seas.
“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,” says co-author Dr. Pierre Dutrieux, an ocean physicist with the British Antarctic Survey. “So it’s a potentially much more rapid and abrupt change.”
Dutrieux adds Pine Island’s ice shelf is important because it helps to hold back this relatively unstable West Antarctic glacier, the way the curved buttresses on Notre Dame cathedral hold up the building’s mass. The researchers warns that if those buttresses are removed, the slow-moving glacier can flow more quickly downward to the ocean.
“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,” Dr. Dutrieux concludes. “Regular advance and break-ups happened at approximately the same location until 2017, and then successively worsened each year until 2020.”
The findings appear in the journal Science Advances.
SWNS writer Stephen Beech contributed to this report.