1980~2007年喜马拉雅东段洛扎地区冰川变化遥感监测

Monitoring glacial variations based on remote sensing in the Luozha region,eastern Himalayas,1980—2007

利用1980年地形图和多年遥感资料,采用目视解译方法手工提取了喜马拉雅东段洛扎地区4个时期的冰川信息,对冰川时空分布特征和变化与不确定性进行了分析,并结合近28年(1980～2007年)的气温、降水量资料对研究区的冰川变化原因进行了研究。结果表明:(1)1980～2007年,洛扎地区冰川面积从491.64 km2减少至410.87 km2,退缩了80.76 km2,占1980年总面积的16.4%;(2)冰川规模等级和面积减少百分比呈反相关关系,该地区1980年面积在1 km2以内的冰川多达236条,占冰川总数量的71.7%,这使得洛扎地区冰川系统对气候变化十分敏感;(3)1980～2007年,主要的冰川消融发生在海拔6500 m以下,面积减少共79.76 km2,占研究区冰川退缩总面积的98.8%,而海拔6500 m以上面积仅减少1km2,占研究区冰川退缩总面积的1.2%;(4)1980～2007年,不同坡度的冰川面积都在减小,低坡度上的消融量比较大而高坡度上消融量比较小;(5)1980～2007年,各个坡向的冰川面积都在减少,但东坡、东南坡、南坡和西南坡冰川消融量大,北坡、东北坡、西坡和西北坡消融量较小;(6)喜马拉雅东段冰川面积退缩速率比中、西段快,喜马拉雅地区冰川退缩比青藏高原腹地的冰川退缩快;(7)1980年以来,气温升高和降水在波动中变化不大是本区冰川退缩的主要原因。

Based on the topographic maps in 1980,1988/1990 Landsat TM,2000 Landsat ETM＋ and 2007 ALOS AVNIR-2 remote sensing data,the glacier boundaries in the Luozha region of eastern Himalayas in the four periods were manually mapped in the false-color image by on-screen digitizing.Spatial-temporal distribution chara and changes of glaciers were analyzed by means of geographical information system and remote sensing technologies.Moreover,the reasons for glacial changes were investigated with the aid of temperature and precipitation data covering that period.The results showed that：（1） From 1980 to 2007,the total glacier area decreased from 491.64 km2 to 410.87 km2.The overall loss was 80.76 km2,or 16.4% of the whole glacial area in 1980.（2） The inverse relationship between initial area and change rate indicated that small glaciers receded faster than big ones.As the number of glaciers with area less than 1 km2 was 236,accounting for 71.7% of the total number of glaciers,the glacier system of Luozha region may be very sensitive to climate change.（3） Glacier melt mainly occurred at area below 6500 m,accounting for 98.8% of the area loss of all the glaciers in the study area.（4） During 1980—2007,the glacier areas reduced on all slopes,while the larger area loss happened on the lower slopes.（5） The area reduction of glaciers facing east,southeast,south and southeast was larger than that of glaciers facing north,northeast,west and northwest during this period.（6） The retreat rate of eastern Himalayan glaciers was faster than that of central and western Himalayas,and the Himalayan glaciers retreated faster than those in the hinterland of the Tibetan Plateau.（7） Finally,rising temperature along with little change in the precipitation in the Luozha region was the main factors that caused glacier retreat.