Bi-polar studies on physical and mechanical properties of deep ice cores

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Polar ice sheets contain palaeo-environmental variation records on the Earth. This study aims to investigate physical and mechanical characteristics of ice sheets by conducting comparative studies of Greenland (GRIP and NGRIP cores) and Antarctic (Dome Fuji core) ice sheets, which serve as a foundation to retrieve environmental signals from deep ice cores. Major outcomes are summerized as below.1) To investigate slip systems of ice crystal, a growth apparatus for a large single ice crystal was designed and constructed in a laboratory in reference to the Czochralski method. Uniaxial compression tests were carried out with ice samples obtained. Flow stress for pyramidal plane sliding is much higher than those hitherto assumed. This suggest that pyramidal plane sliding may not be contributing to ice sheet flow.2) Uniaxial compression tests on deep core samples from GRIP, Greenland and Dome Fuji, Antarctica revealed that ice flow strength depends only on c-axis distribution, and not on impurity contents. This suggests that ice sheet flow strength may be calculated by adopting some models for fabric evolution in ice sheets.3) Microscopic observations on cloudy band structures in ice core samples from NGRIP and GRIP, Greenland revealed that major sources for light scattering are micro-bubbles and the number density and size distribution were measured for the first time.