念青唐古拉山西段冰川1977-2010年时空变化

Glacier Temporal-Spatial Change Characteristics in Western Nyainqentanglha Range,Tibetan Plateau 1977-2010

青藏高原现代冰川变化是对气候变化的响应,对区域水资源评估有着重要的理论意义和现实意义.采用GIS分析方法,利用三期卫星遥感数据研究青藏高原中部念青唐古拉山西段冰川在2个时间段(1977-2001和2001-2010)的时空分布和变化,并对比分析其在南坡和北坡变化速率趋势以及在不同海拔高度的变化特征.研究发现:(1)2010年念青唐古拉山西段冰川面积为571.81±16.01km2,主要分布在5500～6200m的高山区;(2)1977-2010年念青唐古拉山西段冰川退缩明显,总面积减少22.42%±2.90%;(3)相比于1977-2001年时间段,近十年来该区冰川退缩速率呈明显加剧趋势;(4)与前一个时段相比,低于5700m海拔区域,各海拔段的冰川年均面积退缩速率呈减缓趋势;而在5700～7000m海拔区域,则呈加剧趋势;(5)北坡冰川退缩率(23.6%±2.88%)高于南坡(21.97%±2.90%),且南北坡2001-2010年年均冰川面积减少最大的海拔段比1977-2001年都升高了200m,研究区冰川的持续退缩有向高海拔转移的趋势;(6)南坡拉萨河流域内的冰川年均减少面积最大的海拔段比北坡高100m左右.气温升高是影响近十年以来研究区的冰川退缩加剧的根本原因,将对区域水文和生态环境产生重大的影响.

Three atmospheric/topographic corrected Landsat images(acquired form 17/03/1977,05/02/2001,06/02/2010) have been used to map the glacier extents using threshold ratio images(BAND4/BAND5) and ISODATA unsupervised classification,respectively.A few of manual editing was made to correct the outline at ice-lake contacts and at debris covered glaciers.Spatial-temporal distribution and changes of glaciers are analyzed based on GIS and RS.Results show that(1) The glacier in WNR covered 571.81±16.01 km2 in 2010,located mainly at the elevation zone of 5 500-6 200 m;(2) The glacier retreat is obvious in recent three decades,especially in the last decade.The glacier area had decreased by 22.42%±2.90% between 1977 and 2010.(3) Compared to the period 1977-2001,the glacier retreat rate in the last decade is higher.(4) The annual mean reduction of glacier area slows down in the elevation zone of lower 5 700 m,while it speeds up between 5 800-7 000 m.(5) In Lhasa River basin the elevation zone that the glacier reduction fastest is 100 m higher than that in the Namco basin.The Lhasa river basin glacier reduction was affected by the climate change and anthropogenic activities,while the glacier retreat in Namco basin was mainly caused by climate change.(6) The rate of glacier retreat is higher in Namco basin on the northern slope(23.6%±2.88%) of research area than those on the southern slope(21.97%±2.90%).And the elevation zone where the highest rate of glacier retreat during 2001-2010 is 200 m higher than those between 1977 and 2001.It indicates that the glaciers tend to shrink in higher elevation.