2021 年 94 巻 2 号 p. 81-95
We conducted ground penetrating radar (GPR) soundings and geodetic surveys in four perennial snow patches (PSPs) in the northern Japanese Alps (NJA) and considered the possibility that they could be active glaciers. The Kakunezato and Ikenotan PSPs had large ice bodies (>30 m thick) and flow velocities greater than 2 m/a; hence, both PSPs were admissible as active glaciers. Kuranosuke PSP also had a large ice body (25 m thick) but a flow velocity of only 3 cm/a and, therefore, the PSP was admissible as an active glacier that had been shifting to a PSP. Hamaguriyuki PSP was not admissible as a glacier because there was no evidence of a flow under current conditions. As a result of this study and the work of Fukui and Iida (2012), a total of six PSPs in the NJA were admissible as active glaciers. We also investigated the climate conditions, mass balance, and surface area changes of the active glaciers in the NJA based on in situ measurements of air temperature, snow depth, and mass balance, as well as the interpretation of aerial photographs. We found that the mountain ridges of the Tateyama Mountains were slightly higher than the climatic equilibrium line altitude (ELA). Local topographic conditions that led to huge snow accumulations by avalanches were considered likely to alter significantly the ELA of each glacier in the NJA. The Kakunezato and Ikenotan PSPs lost only 12% and 16% of their surface areas between 1955 and 2016, respectively.
