2016 年 34 巻 p. 33-40
This paper outlines meteorological and glaciological observations of Glacier No. 31 in the Suntar-Khayata Range, east Siberia, obtained from 2012 to 2014. We set up meteorological instruments and seven stakes on the glacier for the purpose of measuring surface mass balance and flow velocity. The mean air temperature between July 8, 2012 and August 7, 2013 was －13.9°C at site 31-2 (2446m a.s.l.) and the minimum temperature was －46.0°C. The air temperature on the glacier from November to April was approximately 10°C higher than that at Oymyakon village, suggesting a temperature inversion phenomenon, which typically occurs during winter in this region. The snow depth records show that snow increased at the beginning and end of winter, and that there was almost no change from the beginning of October until the end of April. The maximum snow depth from the previous summer was 158cm at site 31-2 on May 28, 2013. The average annual surface mass balance for the 6sites was －1256mm water equivalent (w.e.) during the period from August 24, 2012 to August 16, 2013, indicating that ablation proceeded rapidly in all areas of the glacier. Surface flow velocity in 2013/2014 was 1.57ma−1 at the approximate midpoint of the glacier, and was much slower than that measured during the IGY (International Geophysical Year) period (4.5ma−1) in 1957/1958. The length and areal extent of the glacier were 3.85km and 3.2km2 in 1958/1959 and 3.38km and 2.27km2 in 2012/2013, respectively, showing a decrease over the last 54years.