MSGID: 1:317/3 640ab26c   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Arctic river channels changing due to climate change    
    Migration pace of large rivers in permafrost regions    
      
     Date:   
         March 9, 2023   
     Source:   
         University of British Columbia Okanagan campus   
     Summary:   
         A team of international researchers have found that the rivers in   
         Arctic Canada and Alaska are not behaving as expected in response   
         to the warming climate. The study focused on large rivers in   
         the region and their movement through permafrost terrain. Their   
         findings highlight the impact of atmospheric warming on these   
         vital waterways.   
      
      
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   FULL STORY   
   ==========================================================================   
   A team of international researchers monitoring the impact of climate   
   change on large rivers in Arctic Canada and Alaska determined that, as   
   the region is sharply warming up, its rivers are not moving as scientists   
   have expected.   
      
      
   ==========================================================================   
   Dr. Alessandro Ielpi, an Assistant Professor with UBC Okanagan's Irving K.   
      
   Barber Faculty of Science, is a landscape scientist and lead author   
   of a paper published this week in Nature Climate Change. The research,   
   conducted with Dr.   
      
   Mathieu Lapo^tre at Stanford University, along with Dr. Alvise Finotello   
   at the University of Padua in Italy, and Universite' Laval's Dr. Pascale   
   Roy- Le'veille'e, examines how atmospheric warming is affecting Arctic   
   rivers flowing through permafrost terrain.   
      
   Their findings, says Dr. Ielpi, were a bit surprising.   
      
   "The western Arctic is one of the areas in the world experiencing the   
   sharpest atmospheric warming due to climate change," he says. "Many   
   northern scientists predicted the rivers would be destabilized by   
   atmospheric warming. The understanding was that as permafrost thaws,   
   riverbanks are weakened, and therefore northern rivers are less stable   
   and expected to shift their channel positions at a faster pace."   
   This assumption of faster channel migration owing to climate change has   
   dominated the scientific community for decades.   
      
   "But the assumption had never been verified against field observations,"   
   he adds.   
      
   To test this assumption, Dr. Ielpi and his team analyzed a collection of   
   time- lapsed satellite images -- stretching back more than 50 years. They   
   compared more than a thousand kilometres of riverbanks from 10 Arctic   
   rivers in Alaska, the Yukon and Northwest Territories, including major   
   watercourses like the Mackenzie, Porcupine, Slave, Stewart and Yukon.   
      
   "We tested the hypothesis that large sinuous rivers in permafrost terrain   
   are moving faster under a warming climate and we found exactly the   
   opposite," he says. "Yes, permafrost is degrading, but the influence of   
   other environmental changes, such as greening of the Arctic, counteracts   
   its effects. Higher temperatures and more moisture in the Arctic mean   
   the region is greening up.   
      
   Shrubs are expanding, growing thicker and taller on areas that were   
   previously only sparsely vegetated."  This growing and robust vegetation   
   along the riverbanks means the banks have become more stable.   
      
   "The dynamics of these rivers reflect the extent and impact of global   
   climate change on sediment erosion and deposition in Arctic watersheds,"   
   Dr. Ielpi and his colleagues write in the paper. "Understanding the   
   behaviour of these rivers in response to environmental changes is   
   paramount to understanding and working with the impact of climate warming   
   on Arctic regions."  Dr. Ielpi points out that monitoring riverbank   
   erosion and channel migration around the globe is an important tool   
   that should be widely used to understand climate change. As part of   
   this research, a dataset of rivers found in non- permafrost regions and   
   representative of warmer climates in the Americas, Africa and Oceania   
   was also analyzed. Those rivers migrated at rates consistent with what   
   was reported in previous studies, unlike those in the Arctic.   
      
   "We found that large sinuous rivers with various degrees of permafrost   
   distribution in their floodplains and catchments, display instead a   
   peculiar range in migration rates," says Dr. Ielpi. "Surprisingly,   
   these rivers migrate at slower rates under warming temperatures."   
   The time-lapse analysis shows that the sideways migration of large   
   Arctic sinuous rivers has decreased by about 20 per cent over the last   
   half-century.   
      
   "The migration deceleration of about 20 per cent of the documented Arctic   
   watercourses in the last half century is an important continent-scale   
   signal.   
      
   And our methodology tells us that 20 per cent may very well be a   
   conservative measure," he says. "We're confident it can be linked to   
   processes such as shrubification and permafrost thaw, which are in turn   
   related to atmospheric warming.   
      
   "Scientific thinking often evolves through incremental discoveries,   
   although great value lies in disruptive ideas that force us to look at   
   an old problem with new eyes," states Dr. Ielpi. "We sincerely hope   
   our study will encourage landscape and climate scientists elsewhere   
   to re-evaluate other core assumptions that, upon testing, may reveal   
   fascinating and exciting facets of our ever-changing planet."   
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   ==========================================================================   
   Story Source: Materials provided by   
   University_of_British_Columbia_Okanagan_campus. Note: Content may be   
   edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Alessandro Ielpi, Mathieu G. A. Lapo^tre, Alvise Finotello,   
      Pascale Roy-   
         Le'veille'e. Large sinuous rivers are slowing down in a warming   
         Arctic.   
      
         Nature Climate Change, 2023; DOI: 10.1038/s41558-023-01620-9   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/03/230309125031.htm   
      
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