Study on glacier shrinkage in the Himalayas under the monsoon

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Glaciers in the Himalayas are sensitive to the global warming and the recent shrinkage is distinct in the world, since most of snow accumulation falls during a summer monsoon season. This study aimed to compare the regional glacier variations and to clarify the mechanism of shrinkage of the monsoon type glaciers. Field studies were carried out in Bhutan, east Himalayas under the strong monsoon effect and Nepal where glaciers have been monitored by us since the 1970s, and semi-arid India was briefly observed. Satellite images were also analyzed.In Bhutan in cooperation with Geological Survey of Bhutan, automatic meteorological data were recorded in glacier areas for two years from OCT 2002 at a station and for a year from SEP 2003 at another. Melting and flow of two debris-covered glaciers were surveyed for two years. The glacier calved terminal ice into a large pro-glacial lake without decrease of flow speed. As the result, glacier thickness decreased and the lake was enlarged, in contrast with another type glacier of which terminal moraine touches to ice terminus. Analysis method of satellite images to obtain distribution of glacier melting was developed on the basis of ground truth.In Nepal in cooperation with Department of Hydrology and Meteorology, glacier variations were surveyed in 2004 since 1999 in Khumbu and Shorong Himals with GPS and a theodolite. Debris-covered Khumbu Glacier has continued thinning. Shrinkage of debris-free small glaciers are accelerating. Benchmarks were prepared for further monitoring of glacier variations.From various analyses, it is recognized that the recent glacier shrinkage is distinct in the west Himalayas and the shrinkage is more remarkable in the east Himalayas under the stronger monsoon.