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

• Published in: Annals of Glaciology
• Main Authors: Miyamoto, Atsushi, Shoji, Hitoshi, Hori, Akira, Hondoh, Takeo, Clausen, Henrik B., Watanabe, Okitsugu
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Glaciological Society
• Subjects: ice core; fabric; a-axis orientation; mechanical property; 452; Greenland; Annals of Glaciology; Greenland ice core; GRIP; Ice Sheet
• Online Access: http://hdl.handle.net/2115/34754; https://doi.org/10.3189/172756405781812501

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.