Science & Technology

Pine Island Glacier’s Ice Shelf Is Ripping Itself Apart – Speeding Up Key Antarctic Glacier

Pine Island Glacier ends in an ice shelf that floats within the Amundsen Sea. These crevasses are close to the grounding line, the place the glacier makes contact with the Antarctic continent. The photograph was taken in January 2010 from the east facet of the glacier, wanting westward. This ice shelf misplaced one-fifth of its space from 2017 to 2020, inflicting the inland glacier to hurry up by 12%. Credit score: Ian Joughin/College of Washington

For many years, the ice shelf serving to to carry again one of many fastest-moving glaciers in Antarctica has steadily thinned. Evaluation of satellite tv for pc photos reveals a extra dramatic course of lately: From 2017 to 2020, giant icebergs on the ice shelf’s edge broke off, and the glacier sped up.

Since floating ice cabinets assist to carry again the bigger grounded mass of the glacier, the latest speedup as a result of weakening edge may shorten the timeline for Pine Island Glacier’s eventual collapse into the ocean. The research from researchers on the College of Washington and British Antarctic Survey was printed on June 11, 2021, within the open-access journal Science Advances.

“We could not have the posh of ready for sluggish adjustments on Pine Island; issues may really go a lot faster than anticipated,” mentioned lead creator Ian Joughin, a glaciologist on the UW Utilized Physics Laboratory. “The processes we’d been learning on this area have been resulting in an irreversible collapse, however at a reasonably measured tempo. Issues might be rather more abrupt if we lose the remainder of that ice shelf.”

The ice shelf on Antarctica’s Pine Island Glacier misplaced about one-fifth of its space from 2017 to 2020, principally in three dramatic breaks. The timelapse video incorporates satellite tv for pc photos from January 2015 to March 2020. For many of the first two years, the satellite tv for pc took high-resolution photos each 12 days; then for greater than three years it captured photos of the ice shelf each six days. Photos are from the Copernicus Sentinel-1 satellites operated by the European House Company on behalf of the European Union. Credit score: Joughin et al./Science Advances

Pine Island Glacier comprises roughly 180 trillion tons of ice — equal to 0.5 meters, or 1.6 ft, of worldwide sea-level rise. It’s already liable for a lot of Antarctica’s contribution to sea-level rise, inflicting about one-sixth of a millimeter of sea-level rise every year, or about two-thirds of an inch per century, a charge that’s anticipated to extend. If it and neighboring Thwaites Glacier velocity up and circulate fully into the ocean, releasing their maintain on the bigger West Antarctic Ice Sheet, world seas may rise by a number of ft over the following few centuries.

These glaciers have attracted consideration in latest a long time as their ice cabinets thinned as a result of hotter ocean currents melted the ice’s underside. From the Nineteen Nineties to 2009, Pine Island Glacier’s movement towards the ocean accelerated from 2.5 kilometers per yr to 4 kilometers per yr (1.5 miles per yr to 2.5 miles per yr). The glacier’s velocity then stabilized for nearly a decade.

Outcomes present that what’s occurred extra not too long ago is a distinct course of, Joughin mentioned, associated to inner forces on the glacier.

From 2017 to 2020, Pine Island’s ice shelf misplaced one-fifth of its space in a couple of dramatic breaks that have been captured by the Copernicus Sentinel-1 satellites, operated by the European House Company on behalf of the European Union. The researchers analyzed photos from January 2015 to March 2020 and located that the latest adjustments on the ice shelf weren’t attributable to processes instantly associated to ocean melting.

“The ice shelf seems to be ripping itself aside as a result of glacier’s acceleration prior to now decade or two,” Joughin mentioned.

Two factors on the glacier’s floor that have been analyzed within the paper sped up by 12% between 2017 and 2020. The authors used an ice circulate mannequin developed on the UW to verify that the lack of the ice shelf brought about the noticed speedup.

“The latest adjustments in velocity should not as a result of melt-driven thinning; as a substitute they’re as a result of lack of the outer a part of the ice shelf,” Joughin mentioned. “The glacier’s speedup just isn’t catastrophic at this level. But when the remainder of that ice shelf breaks up and goes away then this glacier may velocity up quite a bit.”

It’s not clear whether or not the shelf will proceed to crumble. Different components, just like the slope of the land under the glacier’s receding edge, will come into play, Joughin mentioned. However the outcomes change the timeline for when Pine Island’s ice shelf would possibly disappear and how briskly the glacier would possibly transfer, boosting its contribution to rising seas.

“The lack of Pine Island’s ice shelf now appears prefer it probably may happen within the subsequent decade or two, versus the melt-driven subsurface change enjoying out over 100 or extra years,” mentioned co-author Pierre Dutrieux, an ocean physicist at British Antarctic Survey. “So it’s a probably rather more fast and abrupt change.”

Pine Island’s ice shelf is necessary as a result of it’s serving to to carry again this comparatively unstable West Antarctic glacier, the way in which the curved buttresses on Notre Dame cathedral maintain up the cathedral’s mass. As soon as these buttresses are eliminated, the slow-moving glacier can circulate extra rapidly downward to the ocean, contributing to rising seas.

“Sediment data in entrance of and beneath the Pine Island ice shelf point out that the glacier entrance has remained comparatively secure over a couple of thousand years,” Dutrieux mentioned. “Common advance and break-ups occurred at roughly the identical location till 2017, after which successively worsened every year till 2020.”

Reference: “Ice-shelf retreat drives latest Pine Island Glacier speedup” by Ian Joughin, Daniel Shapero, Ben Smith, Pierre Dutrieux and Mark Barham, 11 June 2021, Science Advances.

Different co-authors are Daniel Shapero and Ben Smith on the UW; and Mark Barham at British Antarctic Survey. The research was funded by the U.S. Nationwide Science Basis, NASA and the U.Ok. Pure Surroundings Analysis Council.
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