Ice fabric evolution process understood from anisotropic distribution of a-axis orientation on the GRIP (Greenland) ice core

元データ International Glaciological Society


To better understand how ice fabric evolves in polar ice sheets, we use X-ray diffraction to measure ice crystal orientations. X-ray measurement equipment which can measure the orientation of the c axis and a axis of each crystal in a thin section with high measurement accuracy was developed. In this study, we present a-axes orientation distribution of the deep part of the GRIP (Greenland summit) ice core. At some depths, we find an anisotropic distribution of a-axes orientation. Long-term uniaxial compression tests are also carried out on the GRIP ice core to investigate the ice fabric evolution process. The c-axis orientation distribution develops into a stronger single maximum as the strain increases up to about 20% strain. We find that the a axes of each grain also tend to cluster close to nearly a mutual direction. We discuss the development process of ice fabrics, taking into consideration the distribution of the a-axis orientations. It is suggested that these fabrics may be attributed to a local simple shear deformation in the deep part of an ice sheet.


Watanabe Okitsugu National Institute of Polar Research, Research Organization of Information and Systems
宮本 淳 北海道大学低温科学研究所
本堂 武夫 北大
Miyamoto Atsushi Kitami Institute of Technology
Watanabe O National Institute Of Polar Research Research Organization Of Information And Systems
Watanabe Okitsusgu National Institute of Polar Research
Hori Akira Department Of Materials Science Faculty Of Engineering University Of Tokyo