Study on glacier shrinkage in the Himalayas under the monsoon

喜马拉雅地区的冰川对全球变暖很敏感，最近的退缩在世界范围内是明显的，因为大部分积雪是在夏季季风季节下降的。本研究旨在比较区域冰川变化，阐明季风型冰川萎缩的机制。在不丹、强季风影响下的东喜马拉雅山和尼泊尔进行了实地研究，我们从1970年代开始监测尼泊尔的冰川，并对半干旱的印度进行了短暂观察。还分析了卫星图像。在不丹，与不丹地质调查局合作，在一个观测站和另一个观测站分别记录了从2002年10月到2003年9月的2年和1年冰川地区的自动气象数据。对两个被碎片覆盖的冰川的融化和流动进行了为期两年的调查。冰川将末冰崩解成一个大的前冰湖，流速没有降低。其结果是冰川厚度减小，湖泊面积增大，而另一种类型的冰川则是末碛与冰端接触。在地面真实数据的基础上，提出了利用卫星图像分析冰川融化分布的方法。在尼泊尔与水文和气象部合作，2004年利用GPS和经纬仪调查了自1999年以来昆布和雪山的冰川变化。被碎片覆盖的昆布冰川继续变薄。没有碎片的小冰川正在加速萎缩。为进一步监测冰川变化编制了基准。各种分析表明，在季风较强的条件下，西喜马拉雅地区近期的冰川萎缩明显，东喜马拉雅地区的冰川萎缩更为显著。

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.