Department of Civil Engineering, Kitami Institute of Technology
Institute of Low Temperature Science, Hokkaido University
Institute of Low Temperature Science, Hokkaido University
抄録(英)
Flow behavior of large ice sheets is affected mainly by c-axis orientation fabric, and the fabric formation is caused by the anisotropic characteristics in the plastic deformation property of ice crystal. There are three processes involved in fabric formation; i.e. crystal rotation (AZUMA and HIGASHI, 1985), recrystalization and polygonization. Two types of crystal fabric development with depth have been observed in deep polar ice cores. Type A shows crystal fabric changes from a random distribution near the surface to vertical cluster development with depth under vertical compression and to a strong single maximum pattern near the bottom under simple shear deformation (Camp Century, Dye 3,GRIP and Byrd ice cores). Type B shows fabric changes from a random distribution near the surface to a large girdle development with depth, where the c-axis direction is almost perpendicular to the uniaxial tensile strain axis along the ice flow direction (Mizuho and Vostok ice cores). To estimate vertical compressive strain, ε and uniaxial tensile strain, γ, the following equations were assumed : ε=-ln(y/H), γ=-2ln(y/H), where y is height from the bottom and H is ice thickness. For Type A cores, the c-axis lies mainly along the vertical core direction with depth and a single maximum fabric appears at depth for about ε=150%, except for Byrd core samples which shows single maximum fabric appearance for about ε=80%. For Type B cores, crystal fabrics developments with an increase in γ are quite similar to each other.
雑誌書誌ID
AA10756213
雑誌名
Proceedings of the NIPR Symposium on Polar Meteorology and Glaciology
ICE CRYSTAL ORIENTATION DISTRIBUTIONS IN LARGE ICE MASSES
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KJ00001014953
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概要
