1990—2019年贡嘎山地区典型冰川表碛覆盖变化及其空间差异

Supraglacial debris-cover change and its spatial heterogeneity in the Mount Gongga, 1990-2019

表碛覆盖型冰川是中国西部较为常见的冰川类型。表碛层存在于大气—冰川冰界面,强烈影响大气圈与冰冻圈之间的热交换。表碛厚度的空间异质性可极大地改变冰川的消融率和物质平衡过程,进而影响冰川径流过程和下游水资源。基于Landsat TM/TIRS数据,运用能量平衡方程反演了贡嘎山地区冰川表碛厚度,研究了贡嘎山地区冰川在1990—2019年间表碛覆盖范围及厚度变化情况,同时对比了东西坡差异。结果表明:①贡嘎山地区冰川表碛扩张总面积达43.824 km^(2)。其中,海螺沟冰川扩张2.606 km^(2)、磨子沟冰川1.959 km^(2)、燕子沟冰川1.243 km^(2)、大贡巴冰川0.896 km^(2)、小贡巴冰川0.509 km^(2)、南门关沟冰川2.264 km^(2),年均扩张率分别为3.2%、11.1%、1.5%、0.9%、1.0%和6.5%;②海螺沟冰川、磨子沟冰川、燕子沟冰川、大贡巴冰川、小贡巴冰川、南门关沟冰川表碛平均增厚分别为5.2 cm、3.1 cm、3.7 cm、6.8 cm、7.3 cm和13.1 cm;③西坡冰川表碛覆盖度高,表碛覆盖年均扩张率低,冰川末端退缩量小;东坡冰川表碛覆盖年均扩张率高,但表碛覆盖度总体低于西坡,冰川末端退缩量大。

Debris-covered glaciers are widely distributed in western China.Supraglacial debris lying at the atmosphere-glacier interface plays an important role in the air-ice energy flux and thus influences the underneath ice melt rate.Varying glacier debris thickness will have influence on the mass balance gradient of the debris-covered glacier,the development of ice cliff,ponds and drainage systems,as well as on the downstream runoff process.Using Landsat TM/TIRS images between 1990 and 2019,this study extracted the debris coverage and estimated the thickness changes of the debris-covered glaciers in the Mount Gongga by using a physically-based thermal conductivity method.We found that:(1)The debris coverage of glaciers in the study area totally expanded by 43.824 km^(2),among which the Hailuogou Glacier expanded 2.606 km^(2),Mozigou Glacier 1.959 km^(2),Yanzigou Glacier 1.243 km^(2),Dagongba Glacier 0.896 km^(2),Xiaogongba Glacier 0.509 km^(2) and Nanmenguangou Glacier 2.264 km^(2).Annual expansion rates of their debris covered area are 3.2%,11.1%,1.5%,0.9%,1.0%and 6.5%,respectively.(2)In addition to debris cover area expansion,we found thickening debris layers,with glacier wide average debris thickness increasing by 5.2 cm,3.1 cm,3.7 cm,6.8 cm,7.3 cm and 13.1 cm for the above six mentioned glaciers,respectively.(3)Compared with glaciers on the east slope,debris-covered glaciers on the west slope of the Mount Gongga generally have higher debris cover rate but experienced lower debris cover expansion and lower terminal retreat rate during the past decades.