9:45 AM - 10:00 AM
[ACC29-04] Investigation of internal layering structure and deformation regime at deeper part in the ice sheet by Dome Fuji ice core physical analysis
Keywords:ice core, layering structure, crystal orientation fabric
As a way to investigate the internal structures of ice sheets, there are two ways: direct measurements such as ice core analysis and remote sensing such as radar echo soundings. Each way can provide different types of data regarding the internal structures of ice sheets. Ice core analyses can provide one dimension high-resolution and detailed information at the drilling site. However, ice core drilling is a labor-intensive work and so obtaining ice core is extremely restricted. In contrast, radar echo surveys can provide the internal layering information in large areas with two or three dimensions; however, sometimes the interpretations of radar echoes are difficult. It is not easy to attain high resolutions as high as ice core analysis. For a better understanding of the internal structures in ice sheets, we propose composite approach based on ice cores analyses and radar echo sounding as efficient approach.
Crystal orientation fabric (COF) is one of the important parameters in the ice core analysis. The development of COF highly influences the deformation and flow of ice sheets. To investigate the development and small fluctuation of COF, we measured dielectric anisotropy as indicator of the degree of c-axis clustering. As a result of continuous measurements along an ice core, we found the COF variations associated with transitions from glacial and interglacial periods and concentration of chloride ions and dust particles. Our results indicate that the layering structures formed at near-surface depths is preserved all the way to a deeper part through the deformation. At greater depth, the deformation regime is complicated due to the stress from bedrock, huge crystal grain, and different recrystallization regime due to high temperature.
By obtaining the permittivity profiles in this study, the Dome Fuji ice core becomes the first deep ice core having permittivity and conductivity profiles. These factors are very important in radar echo soundings since they are two major origins causing electromagnetic-wave reflections. By comparing ice core profiles and radar echoes, we can investigate the reflection mechanism in the ice sheet.
In this presentation, we discuss the internal layering structure at the Dome Fuji, the deformation regime at greater depth, and the possibilities of “oldest ice” based on the ice core and radar echo profiles.
Crystal orientation fabric (COF) is one of the important parameters in the ice core analysis. The development of COF highly influences the deformation and flow of ice sheets. To investigate the development and small fluctuation of COF, we measured dielectric anisotropy as indicator of the degree of c-axis clustering. As a result of continuous measurements along an ice core, we found the COF variations associated with transitions from glacial and interglacial periods and concentration of chloride ions and dust particles. Our results indicate that the layering structures formed at near-surface depths is preserved all the way to a deeper part through the deformation. At greater depth, the deformation regime is complicated due to the stress from bedrock, huge crystal grain, and different recrystallization regime due to high temperature.
By obtaining the permittivity profiles in this study, the Dome Fuji ice core becomes the first deep ice core having permittivity and conductivity profiles. These factors are very important in radar echo soundings since they are two major origins causing electromagnetic-wave reflections. By comparing ice core profiles and radar echoes, we can investigate the reflection mechanism in the ice sheet.
In this presentation, we discuss the internal layering structure at the Dome Fuji, the deformation regime at greater depth, and the possibilities of “oldest ice” based on the ice core and radar echo profiles.