takata_etal_2002a.html

Bulletin of Glaciological Research 19 (2002) 19-24
©Japanese Society of Snow and Ice

Stratigraphical structure analysis of the NGRIP shallow ice core using laser tomograph technique

Morimasa TAKATA^1*, Yoshiyuki FUJII², Okitsugu WATANABE² and Hitoshi SHOJI³
1 The Graduate University for Advanced Studies, Kaga 1-9-10, Itabshi-ku, Tokyo 173-8515 Japan
2 National Institute of Polar Research, Kaga 1-9-10, Itabashi-ku, Tokyo 173-8515 Japan
3 Kitami Institute of Technology, Koencho 165, Kitami, Hokkaido 090-8507 Japan
(* Present address: National Institute of Polar Research, Kaga 1-9-10, Itabashi-ku, Tokyo 173-8515 Japan)

Abstract

Stratigraphic features of ice core reflect past seasonal scale conditions of surface snow layers. To detect detailed stratigraphic features of ice core, we develop a new laser tomography method and applied it to NGRIP shallow ice cores for a depth range from 54 to 98 m. By examining the two-dimensional pore distribution, pore ratio and/or pore number obtained with the laser tomograph measurement images, we identified various kinds of layers that were transformed from well-developed depth hoar layers, compacted snow layers and ice crusts. Spectrum analysis of pore ratio fluctuation showed a maximum peak around 0.17 m in water equivalent, which agrees well with the recent annual accumulation rate at the NGRIP site. The present study shows that the laser tomography method has a potential to detect seasonality of stratigraphic features.