A Very Small Glacier on Mt. Chokai, Japan, 1972-1981

With reference to the IASH's classification in World Glacier Inventory (UNESCO/IASH, 1970) and the revised classification by MtiLLER et at. (1977), the author has proposed a type of mountain glacier, the sub-alpine niche glacier formed by abnormally heavy snowfalls and the drifted snow, but not including any kind of avalanche, and named it the “Mount Chokai type glacier” (TsucHIYA, 1978b). During the period 1972-1981, yearly field surveys on the “Kaigata Glacieret, ” one of these types of glaciers, were carried out and the results showed several peculiar features of a very small glacier. Kaigata Glacieret was formed at about 1400m a. s. l., some 2000m below the so called climatic snowline, and covered about 0.04 km2 during a one-year period of development, and then diminished to form tiny ice patches during the course of a few years. The estimated maximum snow depth at the site of this glacier at the end of a snowfall season was about 45m or more. The ablation rate is very high and the observed maximum rate during a warm rainstorm was 1.4cm/h. The rate of glacier ice development was very fast. The density of the remnant snowpack on this glacier coninued to increase almost up to the stage of glacier ice after only one ablation season. The flow rate of the Kaigata Glacieret showed some variation. In the ablation years following accumulation, such as 1975 and 1979, the flow was more rapid. Similar features are recognized on other smaller perennial snow patches (including ice bodies) in the Japanese snowy mountains, but there had been no observational evidences on the flow before 1975. A comparison with similar small glaciers such as the Whakapapanui in New Zealand showed some common features, such as the site of formation being far below the climatic snowline, westerly prevailing winds in the snowfall season, leeward slope fronts at low latitudes, snowdrifts as the main nourishment sources, and large interannual fluctuations.