| The glacier is an important part of the cryosphere, which is considered one of the best natural indicators of climate change. The second China glacier catalog shows, there are 48571 glaciers in China, with a total area of about 51800 km2, which accounts for about 7.1% of the world's glaciers (except Antarctica and Greenland ice sheet). The global average temperature increased by about 0.85 degrees in 1880-2012. The glacier is in a state of sustained retreat under the influence of climate warming. The same trend appears in our country, glaciers have been shrinking over the past few decades, the total glacier area reduced by about 18%. Glacier change has caused glacial lake outburst floods, floods and other related disasters in local glacier flow. This study is based on the Landsat series of remote sensing images in 2000-2015 to analyze the change of glacier area. SRTM data and ZY-3 stereo images are used to study the glacier elevation and ice storage change and the error correction algorithm of remote sensing data obtained from different sources in the upper reaches of Shule River Basin are discussed. The results show that:(1)There are 510 glaciers bigger than 0.01 km2 in 2015, with a total area of 435 km2 in the upper reaches of the Shule River Basin. In the study area, there are 228 glaciers less than 0.1 km2, accounting for about 44.7 % of the total glacier.(2)The study area is divided into three parts for analysis in space. The glacier area is 45 km2 in the northwestern, accounting for about 10.3 % of the total area of the upper reaches of the Shule River basin. The glacier in this region is characterized by its small size and large number. During the period from 2000 to 2015, the glacier area decreased by 21.5 ± 1.0 km2, and the disappearance of the glaciers are mainly smaller than 0.1 km2. The area of glaciers in central part is 342.42 ± 22.64 km2, accounting for about 78.7% of the total area in the upper reaches of the Shule River basin. The glacier area is relatively large, and 6 glaciers are bigger than 10 km2. Glacier changes mainly appear at the edges of the glacier, a total reduction of about 5.4 %. In the southeast, the glacier area accounts for 11% of the total area of glacier, and the number of glaciers is less and the distribution is concentrated.The glacier area was reduced by about 8.95 ± 0.42 km2 during 2000-2015. Overall, 96 glacier disappeared with an area of 57.6 km2 (11.7 %) from 2000 to 2015 in the upper reaches of the Shule River basin.(3)Plane and elevation differences exist in various DEM data, which indicates it is essential to correct errors when glacier surface elevation is compared. It was found that there were match errors between ZY-3 and SRTM, correlation relationship existed in elevation difference and aspect of ZY-3 and SRTM. Therefore,correction equation was established to adjust the elevation error in each stereoscopic pair by relationship diagram established by corresponding elevation difference and aspect.(4) In the upper reaches of the Shule River Basin,the glacier surface elevation generally declined,the elevation is reduced by an average of about 2.58± 0.6 m,with a total reduction of about 1.271±0.307 km3 from 2000 to 2012-2015. It was found that the decline of glacier elevation focus on the edge coverage area and the end of glaciers. The ice elevation change is different in each region at the same time. In northwest glacier, the surface elevation reduced by about 0.19±0.07m on average every year, where glaciers with northeast orientation were prominent; in southeast area, the elevation reduced by about 0.38±0.022m on average every year,where the whole showed a high decline trend; the reduction of glacier mainly appeared in the northwest of glaciers in the central part, which did not show obvious trend of variation; and in the east central region, glaciers elevation showed a tendency to raise with a rate of 0.001±0.047m on average every year. Elevation variation of ice surface reflects the complexity of glacier change. In addition, the ice storage changes calculated by the relationship between area and volume of single glacier are 146.3% higher than those calculated by glacier surface elevation, which indicates that the global ice change estimated by the former may have an overestimation. |
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