11:40 AM - 12:00 PM
[MIS10-10] Permafrost environment in the Daisetsuzan Mountains
★Invited Papers
Keywords:permafrost environment, alpine zone, the Daisetsuzan Mountains, palsa
In the Daisetsuzan Mountains, since permafrost was confirmed around Mt. Koizumi (2158 m a.s.l.) in 1972 (Fukuda and Kinoshita, 1974), permafrost has also been confirmed in the nearby Hokkaidaira (around 2000 m a.s.l.) by geotemperature observations (Sone et al., 1988). On the other hand, in 1985, year-round temperature observations were conducted at an altitude of 2000 m, and the results (annual average temperature -3.8°C) indicated that areas at least 2000 m or more at an altitude were discontinuous permafrost zones. Furthermore, according to Sone et al. (2016), the lower limit of permafrost in the Daisetsuzan Mountains as of 2015 is considered to be around 1755 m above sea level. Topographic evidence suggesting the distribution of permafrost includes frozen fissure polygonal soils (Sone and Takahashi 1986) and palsas (Takahashi and Sone, 1988).
Here, based on previous research, the author reports the observation results of temperature and ground temperature in the alpine zone of the the Daisetsuzan Mountains, and introduces phenomena related to permafrost. In addition, using data from AMeDAS observation points around Daisetsuzan Mountain, the dynamics of permafrost and future predictions will be discussed.
Figure 1 shows the transition of the monthly mean temperature between Koizumidake observation point (2110 m a.s.l.) in the Daisetsuzan Mountains and the Mt. Fujisan summit observation point (3775 m a.s.l.) in 1996~2006. According to the results of these observations, during the period from January to March and from November to December, the temperature at the Koizumidake observation point was lower than that at the Mt. Fujisan summit observation point. The average annual temperatures during this period were -4.4°C and -5.9°C, respectively. This trend is also true for average temperatures in recent years (2018, 2020, 2021). In addition, if the values of the freezing index (2700.6°C・days) and the thawing index (°C・days) for the period 1996~2006 at the Koizumidake observation point are applied to the permafrost classification of Harris (1981), the Koizumidake observation point is located near the boundary between continuous permafrost and discontinuous permafrost.
In recent years, the effects of global warming may have been observed even in the Daisetsuzan Mountains, and the disappearance of palsa has also been confirmed. In particular, precipitation increases during the thaw season (May ~ July) around the Daisetsuzan Mountains, which may be efficiently melting the frozen soil.
Here, based on previous research, the author reports the observation results of temperature and ground temperature in the alpine zone of the the Daisetsuzan Mountains, and introduces phenomena related to permafrost. In addition, using data from AMeDAS observation points around Daisetsuzan Mountain, the dynamics of permafrost and future predictions will be discussed.
Figure 1 shows the transition of the monthly mean temperature between Koizumidake observation point (2110 m a.s.l.) in the Daisetsuzan Mountains and the Mt. Fujisan summit observation point (3775 m a.s.l.) in 1996~2006. According to the results of these observations, during the period from January to March and from November to December, the temperature at the Koizumidake observation point was lower than that at the Mt. Fujisan summit observation point. The average annual temperatures during this period were -4.4°C and -5.9°C, respectively. This trend is also true for average temperatures in recent years (2018, 2020, 2021). In addition, if the values of the freezing index (2700.6°C・days) and the thawing index (°C・days) for the period 1996~2006 at the Koizumidake observation point are applied to the permafrost classification of Harris (1981), the Koizumidake observation point is located near the boundary between continuous permafrost and discontinuous permafrost.
In recent years, the effects of global warming may have been observed even in the Daisetsuzan Mountains, and the disappearance of palsa has also been confirmed. In particular, precipitation increases during the thaw season (May ~ July) around the Daisetsuzan Mountains, which may be efficiently melting the frozen soil.