Internal Structure of Sannomado Glacier, Mt. Tsurugi, Northern Japanese Alps

Abstract

 On September 25-26, 2013, core drilling was conducted at the Sannomado Glacier, Mt. Tsurugi, in the northern Japanese Alps. The ice core obtained is 20 m in length. The ice core consists of a firn layer from the core top to the dirty layer laid down in 2012 (520-532 cm in depth), alternating layers of glacier ice and firn from the dirty layer laid down in 2012 to the dirty layer laid down in 2011 (660-670 cm in depth), and glacier ice from a depth of 660 cm to the core bottom. The glacier ice consists of bubble ice, clear ice, and interbedded dirty layer. Eight distinct dirty layers, estimated to be annual layer boundaries, are found in the core. The Sannomado Glacier is in an environment with extremely thick snow cover in winter and significant snow melt in summer. Analysis of grain size of ice core shows no growth of grain size with icing. Therefore, it is assumed that the glacier ice was formed by dentification of water-saturated firn within two years after snow deposition. Elongated bubbles are more pronounced below 1,278 cm in depth, and the dip of the elongated bubbles is roughly in line with the dip of the glacier flow. These are taken to be evidence that internal deformation is currently occurring in this glacier.