The Ice Shelf of Pine Island Glacier is ripping aside, accelerating Antarctica’s key glacier – Watts Up With That?
VIDEO: THE ICE RULE ON THE PINE ISLAND GLACIER OF THE ANTARCTIC LOST FROM 2017 TO 2020 APPROXIMATELY A FIFTH OF ITS AREA, MOSTLY IN THREE DRAMATIC BREAKS. THE TIME LAPSE VIDEO INCLUDES SATELLITE IMAGES OF… show more
CREDIT: JOUGHIN ET AL./ SCIENTIFIC PROGRESS
For decades, the ice shelf that holds back one of the fastest moving glaciers in Antarctica has been gradually thinning. The analysis of satellite images shows a more dramatic process in recent years: From 2017 to 2020, large icebergs broke off at the edge of the ice shelf and the glacier accelerated.
With floating ice shelves helping to hold back the glacier’s greater grounded mass, the recent acceleration due to the weakening edge could shorten the timeline for the final collapse of the Pine Island Glacier into the sea. The study by researchers from the University of Washington and the British Antarctic Survey was published on June 11 in the open access journal Science Advances.
“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go a lot faster than expected, ”said lead author Ian Joughin, a glaciologist at UW Applied Physics Laboratory. “The processes we studied in this region resulted in an irreversible breakdown, but at a fairly measured pace. Things could get a lot more abrupt if we lose the rest of this ice shelf. “
Pine Island Glacier contains approximately 180 trillion tons of ice – that’s 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 a sixth of a millimeter of sea level rise, or about two-thirds of an inch per century, a rate that is expected to rise. If it and the neighboring Thwaites Glacier accelerate and flow completely into the ocean, loosening their impact on the larger West Antarctic ice sheet, the global seas could rise several meters over the next few centuries.
These glaciers have attracted attention in the past few decades as their ice shelf has thinned because warmer ocean currents melted the bottom of the ice. From the 1990s through 2009, the movement of Pine Island Glacier toward the ocean accelerated from 2.5 kilometers per year to 4 kilometers per year (1.5 miles per year to 2.5 miles per year). The speed of the glacier then stabilized for nearly a decade.
The results show what has happened more recently is a different process, Joughin said, which is related to internal forces on the glacier.
From 2017 to 2020, the Pine Island Ice Shelf lost a fifth of its area due to some dramatic fractures captured by the Copernicus Sentinel-1 satellites operated by the European Space Agency on behalf of the European Union. The researchers analyzed images from January 2015 to March 2020 and found that the recent changes on the ice shelf were not caused by processes directly related to ocean melting.
“The ice shelf appears to be self-rupturing due to the acceleration of the glacier over the past decade or two,” Joughin said.
Two points on the glacier surface that were analyzed in the paper accelerated by 12% between 2017 and 2020. The authors used an ice flow model developed at the UW to confirm that the loss of the ice shelf caused the observed acceleration.
“The recent speed changes are not due to thinning caused by the melt; Instead, they are due to the loss of the outer part of the ice shelf, ”Joughin said. “The acceleration of the glacier is currently not catastrophic. But if the rest of this ice shelf breaks up and disappears, this glacier could accelerate quite a bit. “
It is unclear whether the shelf will continue to crumble. Other factors, like the slope of the land below the receding edge of the glacier, will play a role, Joughin said. But the results change the timeline of when the Pine Island ice shelf might disappear and how fast the glacier might move, increasing its contribution to sea level rise.
“The loss of the Pine Island ice shelf now looks like it could possibly happen in the next decade or two, as opposed to the melt-induced changes in the subsurface that stretch for 100 years or more,” said co-author Pierre Dutrieux , an ocean physicist with the British Antarctic Survey. “So it’s a potentially much faster and more abrupt change.”
The Pine Island Ice Shelf is important because it helps hold back this relatively unstable West Antarctic glacier, just as the curved buttresses of Notre Dame Cathedral hold the bulk of the cathedral. Once these buttresses are removed, the slow-moving glacier can flow into the ocean faster and contribute to the rise of the seas.
“Sediment records in front of and under the Pine Island Ice Shelf show that the glacier front has remained relatively stable for several thousand years,” said Dutrieux. “Until 2017, there was a regular advance and liquidations in roughly the same place, which then gradually worsened every year until 2020.”
Other co-authors are Daniel Shapero and Ben Smith from UW; and Mark Barham of the British Antarctic Survey. The study was funded by the US National Science Foundation, NASA, and the UK Natural Environment Research Council.
Comments are closed.