1990-2015年喜马拉雅山冰川变化的遥感监测及动因分析

采用Landsat TM/ETM+/OLI影像数据,结合比值阈值法与目视解译提取冰川边界,分析了喜马拉雅山冰川在1990-2015年的进退变化。结果表明：近25 a来喜马拉雅山冰川整体呈退缩趋势,冰川面积由23 229.27 km2减少至20 676.17 km2,共减少2 553.10 km2,退缩率为10.99%,研究时段喜马拉雅山冰川加速退缩,尤其是近5 a来,加速退缩的趋势尤为显著。研究区冰川主要分布在海拔4 800~6 200 m范围内,且随着海拔升高冰川分布面积呈先增加后减小趋势,综合分析喜马拉雅山山体海拔特征可知,5 200~5 600 m很可能是研究区的“第二大降水带”。依据山岳冰川分布特征,我们将研究区冰川分为山谷冰川、冰斗冰川、冰斗-山谷冰川、悬冰川和平顶冰川,其中悬冰川的数量最多,山谷冰川的分布面积和平均规模最大。结合研究区周边气象格点数据,同时以12a为滞后期发现,近25a来喜马拉雅山冰川持续退缩很可能是气温升高和降水减少共同作用的结果,且未来十几年内冰川仍可能处于持续退缩的状态。

Glacier Changes in Response to Climate Change in the Himalayas in 1990-2015

Variations in glaciers in response to climate change in the whole Himalayas, which is located in the central southwestern part of the Tibetan Plateau, were investigated using Landsat Thematic Mapper (TM), Enhanced TM Plus (ETM+), Operational Land Imager (OLI), and meteorological data collected over the past 25 years. The results suggest that there were approximately 12 211 glaciers covering an area of 23 229.27 km² in 1990. The total ice cover retreated by approximately 10.99%, with an annual percentage of area change (APAC) of nearly 0.44%/a during the period of 1990-2015. Based on the analysis of meteorological data, glacier shrinkage in the Himalayas can probably be attributed to the increase in air temperature and reduce in precipitation and the glaciers will continue to rapidly shrink in the next several years. The maximum area shrinkage occurred in 2.0-5.0 km² in the Himalayas, with the overall number of glaciers was reduced in the period of 1990-2015, whereas glacier in the size class <0.2 km² increased in area and the total number of glaciers increased significantly over 25 years; The largest glaciers in the area show a maximum elevation of about 5 200-5 600 m in 1990, 2000, 2010 and 2015. All glaciers, regardless of their orientation, have shrunk, but south facing retreated faster than those facing others directions, which indicated that glaciers on this aspect were more sensitive to climate changes in the Himalayas.