Artic Melt Season Lengthens   
       
   April 1, 2014:  A new study by researchers from the National Snow and Ice Data   
   Center (NSIDC) and NASA shows that the length of the melt season for Arctic   
   sea ice is growing by several days each decade. An earlier start to the melt   
   season is allowing the Arctic Ocean to absorb enough additional solar   
   radiation in some places to melt as much as four feet of the Arctic ice cap's   
   thickness.   
       
   "The Arctic is warming and this is causing the melt season to last longer,"   
   said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of   
   the new study, which has been accepted for publication in Geophysical Research   
   Letters. "The lengthening of the melt season is allowing for more of the sun's   
   energy to get stored in the ocean and increase ice melt during the summer,   
   overall weakening the sea ice cover."   
       
   https://www.youtube.com/watch?v=7IQBn-Sg-gc   
       
   A short video summarizes new findings about Arctic sea ice and warming   
   oceans.  Play it!   
       
   Arctic sea ice has been in sharp decline during the last four decades. The sea   
   ice cover is shrinking and thinning, making scientists think an ice-free   
   Arctic Ocean during the summer might be reached this century. The seven lowest   
   September sea ice extents in the satellite record have all occurred in the   
   past seven years.   
       
   To study the evolution of sea ice melt onset and freeze-up dates from 1979 to   
   the present day, Stroeve's team used passive microwave data from NASA's   
   Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor   
   Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried   
   onboard Defense Meteorological Satellite Program spacecraft. When ice and snow   
   begin to melt, the presence of water causes spikes in the microwave radiation   
   that the snow grains emit, which these sensors can detect.   
       
   Results show that although the melt season is lengthening at both ends, with   
   an earlier melt onset in the spring and a later freeze-up in the fall, the   
   predominant phenomenon extending the melting is the later start of the freeze   
   season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up   
   between six and 11 days later per decade. Although melt onset variations are   
   smaller, the timing of the beginning of the melt season has a larger impact on   
   the amount of solar radiation absorbed by the ocean, because its timing   
   coincides with when the sun is higher and brighter in the Arctic sky.   
       
   Despite large regional variations in the beginning and end of the melt season,   
   the Arctic melt season has lengthened on average by five days per decade from   
   1979 to 2013.   
       
   Visit nasa.gov for more information about this research   
       
   Credits:   
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
       
   Regards,   
       
   Roger   
      
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