MSGID: 1:317/3 641a846b   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    3000+ billion tons of ice lost from Antarctic Ice Sheet over 25 years   
      
      
     Date:   
         March 21, 2023   
     Source:   
         University of Leeds   
     Summary:   
         Scientists have calculated that the fastest changing Antarctic   
         region?- ?the Amundsen Sea Embayment?-?has lost more than 3,000   
         billion tonnes of ice over a 25-year?period.??   
      
         Facebook Twitter Pinterest LinkedIN Email   
   FULL STORY   
   ==========================================================================   
   Scientists have calculated that the fastest changing Antarctic   
   region -  the Amundsen Sea Embayment - has   
   lost more than 3,000 billion tonnes of ice over a   
   25-year period.     
      
   ==========================================================================   
   If all the lost ice was piled on London, it would stand over   
   2 km tall - or 7.4 times the height of the Shard. If it   
   were to cover Manhattan, it would stand at 61 km - or 137 Empire   
   State Buildings placed on top of one another.  Twenty major   
   glaciers form the Amundsen Sea Embayment in West Antarctica, which   
   is more than four times the size of the UK, and they play a key   
   role in contributing to the level of the world's oceans.     
    So much water is held in the snow and ice, that if it were to   
   all to drain into the sea, global sea levels could increase by more   
   than one metre.   The research, led by Dr Benjamin   
   Davison at the University of Leeds, calculated the "mass balance"   
   of the Amundsen Sea Embayment. This describes the balance between mass   
   of snow and ice gain due to snowfall and mass lost through calving,   
   where icebergs form at the end of a glacier and drift out to sea.   
      
   When calving happens faster than the ice is replaced by snowfall, then   
   the Embayment loses mass overall and contributes to global sea level rise.   
      
   Similarly, when snowfall supply drops, the Embayment can lose mass   
   overall and contribute to sea level rise.   
      
   The results show that West Antarctica saw a net decline of 3,331   
   billion tonnes of ice between 1996 and 2021, contributing over   
   nine millimetres to global sea levels.  Changes in   
   ocean temperature and currents are thought to have been the most   
   important factors driving the loss of ice.  Dr Davison, a Research   
   Fellow at the Institute for Climate and Atmospheric Science at Leeds,   
   said: "The 20 glaciers in West Antarctica have lost an   
   awful lot of ice over the last quarter of a century and there   
   is no sign that the process is going to reverse anytime soon although   
   there were periods where the rate of mass loss did ease slightly.    
   "Scientists are monitoring what is happening in the Amundsen   
   Sea Embayment because of the crucial role it plays in   
   sea-level rise.   
      
   If ocean levels were to rise significantly in future years, there   
   are communities around the world who would experience extreme   
   flooding."  The research has been published in the scientific   
   journal Nature Communications.   
      
   Extreme snowfall events Using climate models that show how   
   air currents move around the world, the scientists identified that   
   the Amundsen Sea Embayment had experienced several extreme   
   snowfall events over the 25-year study period.  These   
   would have resulted in periods of heavy snowfall and periods of very   
   little snowfall or a "snow drought."   The researchers   
   factored these extreme events into their calculations.   
      
   Surprisingly, they found that these events contributed up   
   to half of the ice change at certain times, and therefore played a   
   key role in the contribution the Amundsen Sea Embayment was making   
   to sea level rise during certain time periods.     
   For example, between 2009 and 2013, the models revealed a period   
   of a persistant snow drought. The lack of snowfall starved the ice   
   sheet and caused it to lose ice, therefore contributing about 25%   
   more to sea level rise than in years of average snowfall.    
   In contrast, during the winters of 2019 and 2020 there   
   was very heavy snowfall. The scientists estimated that   
   this heavy snowfall mitigated the sea level contribution from the   
   Amundsen Sea Embayment, reducing it to about half of what it would have   
   been in an average year.   Dr Davison said:   
   "Changes in ocean temperature and circulation appear to be driving   
   the long-term, large-scale changes in West Antarctica ice sheet   
   mass.  We absolutely need to research those more because   
   they are likely to control the overall sea level contribution from   
   West Antarctica.   "However, we were really surprised to   
   see just how much periods of extremely low or high snowfall could   
   affect the ice sheet over two to five-year periods - - so much so   
   that we think they could play an important, albeit secondary role, in   
   controlling rates of West Antarctic ice loss."  Dr Pierre Dutrieux,   
   a scientist at the British Antarctic Survey and co-author of the study,   
   added: "Ocean temperature changes and glacial dynamics appear   
   strongly connected in this part of the world, but this work highlights   
   the large variability and unexpected processes by which snowfall also   
   plays a direct role in modulating glacier mass."  New glacier named The   
   ice loss from the region over the past 25 years has seen   
   the retreat of the Pine Island Glacier,  also known as PIG.   
      
   As it retreated, one of its tributary glaciers became   
   detached from the main glacier and rapidly accelerated. As   
   a result, the tributary glacier has now been named   
   by the UK Antarctic Place-names Committee, Piglet Glacier, so   
   that it can be unambiguously located and identified by   
   future studies.   Dr Anna Hogg, one of the authors   
   of the paper and Associate Professor at the Institute of Climate   
   and Atmospheric Science at Leeds, said: "As well as shedding   
   new light on the role of extreme snowfall variability on ice sheet   
   mass changes, this research also provides new estimates of   
   how quickly this important region of Antarctica is contributing to   
   sea level rise.   "Satellite observations have showed that the   
   newly named Piglet Glacier accelerated its ice speed by   
   40%, as the larger PIG retreated to its smallest extent since   
   records began."   Satellites such as the Copernicus   
   Sentinel-1 satellite, which uses sensors that 'see'   
   through cloud even during the long Polar night, have transformed our   
   ability to monitor remote regions. It is essential to have   
   frequent measurements of change in ice speed and iceberg calving,   
   so that we can monitor the incredibly rapid change taking place   
   in Antarctica.    
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Global_Warming # Snow_and_Avalanches # Climate #   
                   Ice_Ages   
             o Fossils_&_Ruins   
                   # Early_Climate # Ancient_DNA # Evolution # Fossils   
       * RELATED_TERMS   
             o Ice_sheet o Paleoclimatology o Ice_age o Greenland_ice_sheet   
             o Larsen_Ice_Shelf o Antarctic_krill o Antarctic_ice_sheet   
             o Sea_level   
      
   ==========================================================================   
   Story Source: Materials provided by University_of_Leeds. Note: Content   
   may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Benjamin J. Davison, Anna E. Hogg, Richard Rigby, Sanne Veldhuijsen,   
      Jan   
         Melchior van Wessem, Michiel R. van den Broeke, Paul R. Holland,   
         Heather L. Selley, Pierre Dutrieux. Sea level rise from   
         West Antarctic mass loss significantly modified by large   
         snowfall anomalies. Nature Communications, 2023; 14 (1) DOI:   
         10.1038/s41467-023-36990-3   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/03/230321112644.htm   
      
   --- up 1 year, 3 weeks, 1 day, 10 hours, 50 minutes   
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)   
   SEEN-BY: 15/0 106/201 114/705 123/120 153/7715 226/30 227/114 229/110   
   SEEN-BY: 229/111 112 113 307 317 400 426 428 470 664 700 292/854 298/25   
   SEEN-BY: 305/3 317/3 320/219 396/45   
   PATH: 317/3 229/426