MSGID: 1:317/3 6459cc65   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Researchers discover a cause of rapid ice melting in Greenland    
    Study suggests extent of future sea level rise could be vastly   
   underestimated    
      
     Date:   
         May 8, 2023   
     Source:   
         University of California - Irvine   
     Summary:   
         While conducting a study of Petermann Glacier in northwest   
         Greenland, researchers 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.   
      
      
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   FULL STORY   
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   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 -- 2 1/2 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.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Global_Warming # Climate # Oceanography #   
                   Ice_Ages # Snow_and_Avalanches # Geography # Water #   
                   Environmental_Awareness   
       * RELATED_TERMS   
             o Greenland_ice_sheet o Ice_shelf o Ice_sheet o Larsen_Ice_Shelf   
             o Ice_age o Glacier o Sea_level o Antarctic_ice_sheet   
      
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   Story Source: Materials provided by   
   University_of_California_-_Irvine. Note: Content may be edited for style   
   and length.   
      
      
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   Journal Reference:   
      1. Enrico Ciraci`, Eric Rignot, Bernd Scheuchl, Valentyn Tolpekin,   
      Michael   
         Wollersheim, Lu An, Pietro Milillo, Jose-Luis Bueso-Bello,   
         Paola Rizzoli, Luigi Dini. Melt rates in the kilometer-size   
         grounding zone of Petermann Glacier, Greenland, before and during   
         a retreat. Proceedings of the National Academy of Sciences, 2023;   
         120 (20) DOI: 10.1073/pnas.2220924120   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230508190559.htm   
      
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