1991—2017年叶尔羌河流域冰川景观格局时空演变

Spatio-temporal evolution of glacier landscape pattern in the Yarkant River Basin from 1991 to 2017

冰川景观变化是全球环境和气候变化的共同“指示器”。随着全球气候变化加剧,干旱和半干旱地区的冰川景观将进一步变化。科学评估冰川景观格局时空演变特征,为应对冰川景观变化及其影响提供科学参考。基于1991—2017年Landsat TM/ETM+/OLI遥感影像,采用监督分类方法获取叶尔羌河流域冰川景观时空格局及变化数据,利用景观格局指数、质心迁移模型、分形维数等方法分析近26年叶尔羌河流域冰川景观格局时空演变特征。结果表明:(1) 1991—2017年叶尔羌河流域冰川斑块面积呈消减趋势,但有所减缓,共减少799.50 km^(2)(-13.09%)。冰川斑块面积消减主要集中在海拔5400—5800 m之间,相较之下,海拔4400 m以下的区域冰川斑块面积消减率最高,达63.68%;不同坡度冰川景观消减率存在差异,陡坡冰川斑块面积消减率最高(15.98%),急陡坡消减率最低(2.87%);阴阳两坡冰川景观均呈消减趋势,阳坡冰川斑块面积消减速率显著高于阴坡。(2)近26年来,叶尔羌河流域冰川斑块数量、最大斑块指数均减小,而平均形状指数、平均周长面积比、分裂指数均增加,表明冰川景观不断消减,破碎化程度增加。(3)研究期间,叶尔羌河流域冰川景观质心发生迁移,整体呈现东北偏移趋势。(4)通过分形理论对叶尔羌河流域冰川景观空间结构特征进行分析表明,该流域冰川景观消减率略微降低,但仍然处于持续消融状态。

Glacier landscape change is a common sensitivity indicator of global environmental and climate change. In arid and semiarid climate areas, the glacier landscape will change further due to the intensification of global climate change. To scientifically evaluate the temporal and spatial evolution characteristics of glacier landscape pattern, which can provide scientific reference for coping with glacier landscape change and its impact. Based on Landsat TM/ETM+/OLI remote sensing images from 1991 to 2017, the temporal and spatial pattern and change data of glacier landscape in the Yarkant River Basin were obtained by using the supervised classification method. In addition, the temporal and spatial evolution characteristics of glacier landscape pattern in the Yarkant River Basin in 1991—2017 were analyzed by means of landscape pattern index, mass center migration and fractal dimension. The results showed that:(1) From 1991 to 2017, the glacier patch area in the Yarkant River Basin showed a decreasing trend, but the melting rate slowed down, with a total reduction of 799.50 km^(2)(-13.09%). The decrease of glacier patch area was mainly concentrated at elevations of 5400—5800 m a.s.l. By contrast, the area below the altitude of 4400 m had the highest retreat rate of glacier patch area, which reached 63.68%. There were differences in glacier landscape reduction rates among different slopes. The retreat rate of glacier landscape on steep slope was the highest(15.98%) and that on sharp steep slope was the lowest(2.87%). Glacier landscape on both shady slope and sunny slope showed a trend of retreat, and the reduction rate of glacier patch area on the sunny slope was significantly higher than that on the shady slope.(2) The number of patches and the largest patch index of the glacier in the Yarkant River Basin have decreased, while the mean shape index, the mean perimeter area ratio and the splitting index have increased. As a result, the glacier landscape has been melting and the degree of fragmentation has increased.(3) During the study period, the centroid of the glacier landscape in the Yarkant River Basin migrated, and the overall trend of northeast migration occurred, indicating that the large patch glaciers were mainly distributed in the northeast and the glacier landscape was decreasing.(4) Based on the fractal theory, we analyzed the spatial structure characteristics of the glacier landscape in the Yarkant River Basin, the results showed that the glacier landscape decline rate decreased slightly, but it was still in a continuous melting state.