[A-CC26] Ice cores and paleoenvironmental modeling

[ACC26-04] Layering structures and deformation regime at the deeper part of Dome Fuji –Investigations of physical layering strucutres leading to Oldest ice–

*Tomotaka Saruya¹, Atsushi Miyamoto², Shuji Fujita^1,3, Iizuka Yoshinori⁴, Hiroshi Ohno⁵, Akira Hori⁵, Wataru Shigeyama³, Motohiro Hirabayashi¹, Kumiko Goto-Azuma^1,3, Shun Tsutaki^1,3 (1.National Institute of Polar Research, 2.Institute for the Advancement of Graduate Education, Hokkaido University, Sapporo, 3.The Graduate University for Advanced Studies (SOKENDAI), 4.Institute of Low Temperature Science, Hokkaido University, 5.Kitami Institute of Technology)

Keywords:Dome Fuji ice core, layering structure, deformation regime

Investigations of the layering structures and the state of ice at the deeper parts in ice sheets are important for the understanding of “Oldest ice” in next deep ice core drilling project in the Dome Fuji (DF3). Previous studies based on the ice core analysis and ice radar experiments in the Dome Fuji drilling site revealed that 1) the layering structures are inclined at deeper parts, 2) the temperature is increased with increasing depth and ice body is partially melted near the bedrock. Layering structures and deformation regime of ice at deeper parts might be complicated by these factors.
In the physical properties of ice-sheet ice, the crystal orientation fabric (COF) is one of the important parameters since the development of COF highly affects the deformation and flow of ice sheets. At depths shallower than 2400 m in the Dome Fuji ice core, layering structures of the COF are investigated by author’s group. They revealed that 1) the degree of c-axis clustering in warmer periods is decreased and 2) the factors determining the deformation of ice include the concentration of chloride ions and the amount of dust particles.
To understand the layering structures and deformation regime at deeper part in the ice sheet, we performed physical analyses using the Dome Fuji ice core at depths greater than 2400 m. From the dielectric tensor measurements and microstructural observations using ice thin sections, we found that the development regime of the COF was changed significantly around 2400 m depth. Additionally, the variation trend of the COF associated with the increase of dust particle concentration was changed at deeper parts. These results indicates that the deformation regimes at deeper part are greatly different from those at shallower parts due to the influence of bedrock.