Study suggests extent of future sea level rise could be vastly underestimated
In the center of this NASA photograph taken in 2012,
Petermann Glacier in northwest Greenland gradually moves toward the ocean, with
large segments breaking off and drifting away as icebergs. Researchers at UCI
and NASA JPL used satellite data from three European missions to learn how warm
ocean water is causing the migration of the glacier’s grounding line, leading
to its rapid deterioration. NASA
Irvine, Calif., May 8, 2023 – While conducting a study of Petermann Glacier in northwest Greenland,
researchers at the University of California, Irvine and NASA’s Jet Propulsion
Laboratory uncovered a previously unseen way in which the ice and ocean
interact. The glaciologists said their findings could mean that the climate
community has been vastly underestimating the magnitude of future sea level
rise caused by polar ice deterioration.
Using satellite radar data from three
European missions, the UCI/NASA team learned that Petermann Glacier’s grounding
line – where ice detaches from the land bed and begins floating in the ocean –
shifts substantially during tidal cycles, allowing warm seawater to intrude and
melt ice at an accelerated rate. The group’s results are the subject of a paper
published in Proceedings of the National Academy of Sciences.
“Petermann’s grounding line could be
more accurately described as a grounding zone, because it migrates between 2
and 6 kilometers as tides come in and out,” said lead author Enrico Ciraci, UCI
assistant specialist in Earth system science and NASA postdoctoral fellow.
“This is an order of magnitude larger than expected for grounding lines on a
rigid bed.”
He said the traditional view of
grounding lines beneath ocean-reaching glaciers was that they did not migrate
during tidal cycles, nor did they experience ice melt. But the new study
replaces that thinking with knowledge that warm ocean water intrudes beneath
the ice through preexisting subglacial channels, with the highest melt rates
occurring at the grounding zone.
The researchers found that as Petermann
Glacier’s grounding line retreated nearly 4 kilometers – 2½ miles – between
2016 and 2022, warm water carved a 670-foot-tall cavity in the underside of the
glacier, and that abscess remained there for all of 2022.
“These ice-ocean interactions make the
glaciers more sensitive to ocean warming,” said senior co-author Eric Rignot,
UCI professor of Earth system science and NASA JPL research scientist. “These
dynamics are not included in models, and if we were to include them, it would
increase projections of sea level rise by up to 200 percent – not just for
Petermann but for all glaciers ending in the ocean, which is most of northern
Greenland and all of Antarctica.”
The Greenland ice sheet has lost
billions of tons of ice to the ocean in the past few decades, the PNAS paper
stresses, with most of the loss caused by warming of subsurface ocean waters, a
product of Earth’s changing climate. Exposure to ocean water melts the ice
vigorously at the glacier front and erodes resistance to the movement of
glaciers over the ground, causing the ice to slide more quickly to the sea,
according to Rignot.
Ciraci’s research was supported by the NASA Postdoctoral Program at the Jet Propulsion Laboratory. Joining Ciraci and Rignot on the project were Bernd Scheuchl, UCI associate project scientist; Valentyn Tolpekin and Michael Wollersheim of Finland’s Iceye mission; Lu An of China’s Tongji University; Pietro Milillo of the University of Houston; Jose-Luis Bueso-Bello of the German Aerospace Center; and Luigi Dini of the Italian Space Agency.
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Source: UC
Irvine, NASA JPL researchers discover a cause of rapid ice melting in Greenland
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