2:00 PM - 2:15 PM
[ACC26-02] Analysis of Dome Fuji ice core fabric by dielectric tensor measurement
★Invited Papers
Keywords:ice-sheet core, crystal orientation fabric, dielectric tensor
Crystal orientation fabric (COF) is one of the most important factors determining the physical properties of polar ice sheets. The orientation of the c-axis is commonly determined from thin ice sections using automatic crystal fabric analyzers based on optical techniques. Recent advance of the automated fabric analyzers improved the quality of measurements dramatically; however, there are still limitations. Obtaining a continuous COF profile along a lengthy ice core section requires the labor-intensive preparation of many thin sections. Accordingly, the sampling frequency along an ice core is often limited, with typical sampling intervals of at least 5 or 10 m.
To conduct the bulk-ice-core based fabric measurements, we developed a new system by measuring tensorial components of the dielectric permittivity using an open resonator. Polycrystalline ice is known to exhibit macroscopic anisotropy in dielectric permittivity depending on the formation of a crystal orientation fabric. By measuring the macroscopic dielectric property of ice core, we can estimate the degree of c-axis clustering. This technique permits the continuous nondestructive assessment of the COF in thick ice sections.
Using a new system, we investigated the dielectric anisotropy as indicator of COF in Dome Fuji ice core. From measurements with vertical slab sections, we found the increase of dielectric anisotropy around the core axis with increasing depth, supporting previous findings that c-axes cluster around the vertical direction. Analyses of horizontal disk sections showed that the magnitude of dielectric anisotropy in the horizontal plane was 10–15% of that in the vertical plane. We confirmed that the dielectric anisotropy adequately represents preferred orientation of the c-axes, and that the anisotropy can be used as substitute of the normalized eigenvalue of COF. In this presentation, we discuss the depth variation of dielectric anisotropy and correlations with other physical and chemical properties.
To conduct the bulk-ice-core based fabric measurements, we developed a new system by measuring tensorial components of the dielectric permittivity using an open resonator. Polycrystalline ice is known to exhibit macroscopic anisotropy in dielectric permittivity depending on the formation of a crystal orientation fabric. By measuring the macroscopic dielectric property of ice core, we can estimate the degree of c-axis clustering. This technique permits the continuous nondestructive assessment of the COF in thick ice sections.
Using a new system, we investigated the dielectric anisotropy as indicator of COF in Dome Fuji ice core. From measurements with vertical slab sections, we found the increase of dielectric anisotropy around the core axis with increasing depth, supporting previous findings that c-axes cluster around the vertical direction. Analyses of horizontal disk sections showed that the magnitude of dielectric anisotropy in the horizontal plane was 10–15% of that in the vertical plane. We confirmed that the dielectric anisotropy adequately represents preferred orientation of the c-axes, and that the anisotropy can be used as substitute of the normalized eigenvalue of COF. In this presentation, we discuss the depth variation of dielectric anisotropy and correlations with other physical and chemical properties.