Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS) in an attempt to understand the processes that control their behavior. Glaciers over the recent 40 years(1970-2010) have shrunk 3.4±3.1%in area, based on a comparison between two Chinese glacier inventories. Variations of surface elevations, derived from ICESat-GLAS(Ice, Cloud, and Land Elevation Satellite-Geoscience Laser Altimeter System) elevation products(GLA14 data) using the robust linear-fit method, indicate that the glaciers have been gaining mass at a rate of 0.23±0.24 m w.e./a since 2003. The annual mass budget for the whole WKS range from 2003 to 2009 is estimated to be 0.71±0.62 Gt/a. This gain trend is confirmed by MOD10A1 albedo for the WKS region which shows a descent of the mean snowline altitude from 2003 to 2009.
In the Tibetan Plateau, many glaciers have extensive covers of supraglacial debris in their ablation zones, which affects glacier response to climate change by altering ice melting and spatial patterns of mass loss. Insufficient debris thickness data make it difficult to analyze regional debris-cover effects. Maritime glaciers of the Mount Gongga have been characterized by a substantial reduction in glacier area and ice mass in recent decades. The thermal property of the debris layer estimated from remotely sensed data reveals that debris-covered glaciers are dominant in this region, on which the proportion of debris cover to total glacier area varies from 1.74% to 53.0%. Using a physically-based debris-cover effect assessment model, we found that although the presence of supraglacial debris has a significant insulating effect on heavily debris-covered glaciers, il accelerates ice melting on -10.2% of total ablation zone and produces rapid wastage of -25% of the debris-covered glaciers, leading to the similar mass losses between the debris-covered and debris-free glaciers. Widespread debris cover also facilitates the development of active terminus regions. Regional differences in debris-cover effects are apparent, highlighting the im- portance of debris cover for understanding glacier mass changes in the Tibetan Plateau and other mountain ranges around the world.
ZHANG YongHIRABAYASHI YukikoFUJITA KojiLIU Shi YinLIU Qiao
Glaciers in the western Nyainqentanglha Range are an important source of water for social and economic development. Changes in their area were derived from two Chinese glacier inventories; one from the 197o 1：5o,ooo scale Chinese Topographic Maps series and the other from Landsat TM/ETM＋ images acquired in 2009. Analyses also included boundaries from 2000 and 2014 Landsat TM/ETM＋ images. A continuing and accelerating shrinkage of glaciers occurred here from 1970 to 2014, with glacier area decreasing by 244.38±29.48 km^2 （27.4%±3.3%） or 0.62%±0.08% a^-1. While this is consistent with a changing climate, local topographic parameters, such as altitude, slope, aspect and debris cover, are also important influences. Recession is manifested by a rise in the elevation of the glacier terminus. The shrinkage of glaciers with NE, N and NW orientations exceeded that of other aspects, and glaciers with SE and S orientations experienced less shrinkage. Changes in the average positive difference of glaciation （PDG） show that the western Nyainqentanglha Range has unfavorable conditions for glacier maintenance which is being exacerbated by a warming climate since 1970.
Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region.In the last 50 years,these glaciers have shrunk and lost ice mass due to climate change.In order to understand recent glacier dynamics in the region,a new inventory was compiled from Landsat TM/ETM+ images acquired in2009,free of clouds and with minimal snow cover on the glacierized mountains.The first glacier inventory of the area was also updated by digitizing glacier outlines from topographical maps that had been modified and verified using aerial photographs.Total glacier area decreased by 10.8%±1.1%,mainly attributed to an increase in air temperature,although precipitation,glacier size and topographic features also combined to affect the general shrinkage of the glaciers.The 19.3–21.4 km^3 estimated glacier mass loss has contributed to an increase in river runoff and water resources.
Glacier retreat is not only a symbol of temperature and precipitation change, but a dominating factor of glacial lake changes in alpine regions, which are of wide concern for high risk of potential outburst floods. Of all types of glacial lakes, moraine-dammed lakes may be the most dangerous to local residents in mountain regions. Thus, we monitored the dy- namics of 12 moraine-dammed glacial lakes from 1974 to 2014 in the Poiqu River Basin of central west Himalayas, as well as their associated glaciers with a combination of remote sensing, topographic maps and digital elevation models （DEMs）. Our results indicate that all monitored moraine-dammed glacial lakes have expanded by 7.46 km2 in total while the glaciers retreated by a total of 15.29 km2 correspondingly. Meteorological analysis indicates a warming and drying trend in the Nyalam region from 1974 to 2014, which accelerated glacier retreat and then augmented the supply of moraine-dammed glacial lakes from glacier melt. Lake volume and water depth changed from 1974 to 2014 which indicates that lakes Kangxico, Galongco, and Youmojanco have a high potential for outburst floods and in urgent need for continuous moni- toring or artificial excavation to release water due to the quick increase in water depths and storage capacities. Lakes Jialongco and Cirenmaco, with outburst floods in 1981 and 2002, have a high potential risk for outburst floods because of rapid lake growth and steep slope gradients surrounding them.
