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第 136 回 大気海洋物理系 B 棟コロキウム のおしらせ

日　時：2002年 7月 15日(月) 午後 16:30 〜 18:30
場　所：地球環境科学研究科 Ｃ棟 Ｃ１０４

発表者：Jennifer Engels (Department of Geology and Geophysics, University of Hawaii at Manoa)
題　目：Ice scours in the Chukchi borderland, Arctic Basin:dynamics of sea ice break-up

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Ice scours in the Chukchi borderland, Arctic Basin:dynamics of sea ice break-up (Jennifer Engels) 発表要旨 :

  
       The Chukchi borderland was the subject of a comprehensive geophysical 
 survey by the SCICEX-99 expedition aboard the unclear submarine  
 USS Hawkbill in 1999, and the resultant 12kHz swath bathymetry and  
 sidescan sonar data show clear evidence for the progressive collapse 
  of a large ice shelf or shelves. Distinctive ice scours at discrete 
 extending up to 700m deep, to megabergs driven by currents in an 
 ice-bound ocean, and finally to small icebergs moving randomly 
 according to wind or current patterns across the crest of the Chukchi 
 Plateau. 
 	At 700m depth in the Chukchi borderland, evenly spaced  
 parallel flutes measuring 30m wide and 1km long trend northwest, 
 extending seaward from the Alaskan continental margin as evidenced 
 by drumlin features. We believe these flutes are the traces of 
 Alaskan/Canadian ice streams flowing west, deflected north by the 
 steep Alaskan continental shelf. Morainic and ice-marginal features  
 found in conjunction with ice flutes indicate depths of progressive 
 ice shelf retreat. Randomly oriented scours at depths of 350-400m 
 overprint flutes on the crest of the Chukchi plateau and are 
 characteristic of the unrestricted movement of small icebergs in the  
 wake of large-scale ice surges. Stratigraphic age controls on these 
 ice features are as yet incomplete, but new technology for geophysical 
 surveying in ice-covered oceans has allowed us for the first time to 
 reconstruct a portion of the paleo-ice history of the Chukchi 
 borderland region.   
  
  

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