[A-CC25] 雪氷学

[ACC25-05] 非定常モデリングによるモンゴルの境界永久凍土マッピング

*石川 守¹、Westermann Sebastian²、Jambaljav Yamkhin³、Avirmed Dashtseren³、Bernd Etzelmueller² (1.北海道大学、2.オスロ大学地球科学系、3.モンゴル科学アカデミー地理地生態研究所)

キーワード：境界永久凍土、非定常モデリング、モンゴル

Permafrost distribution over the southernmost marginal zones is highly complicated both in time and space. We evaluated this complexity through applying transient heat transfer schemes that reconstructed the distribution of Mongolian permafrost from 1979 to 2016. The modelling considered spatiality of soil thermal properties determined according to diverse landcovers using 1-dimensional heat transfer scheme and time-series of ground temperature profiles at 69 local borehole sites. Spatial modelling was forced by downscaled ERA5 air temperatures that were further calibrated with local meteorological records. The results indicated that permafrost warmed by 0 to 0.04 ^oC/year most significantly in the eastern and northern Hangai, and high elevations of Altay Mountains. The permafrost areas were remained almost stable during the period while active layer thickness has increased especially after the late 1990. Tree covered wet soils did not warm while soils with less organic and water warmed significantly by 0.5 ^oC. Estimated lower limits of mountain permafrost were ranged between 1320 to 2030 mASL, which have shifted upward by 9 to 20 m from the 1980s to 2010s. Comparing our permafrost map with others by diverse modelling schemes, we found that marginal permafrost of Mongolia shows both features of mountain and circumpolar permafrost, depending heavily on localities of vegetation and topographic undulation that contribute to cause strong atmospheric inversion during wintertime.