*通信作者:杨太保(1962-),男,山西运城人,教授,主要从事自然地理环境变化的研究.E-mail:yangtb@lzu.edu.cn

Remote Sensing Monitoring of Glacier Changes in the Western Region of Tanggula Mountains in Recent 25 Years
Wang Congqiang, Yang Taibao*, Xu Aiwen, Ji Qin, Mihretab G. Ghebrezgabher
College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China

First author:Wang Congqiang(1989-), male, Pingdingshan City,He’nan Province, Master student. Research areas include global and environmental change. E-mail:15101229024@163.com

*Corresponding author:Yang Taibao(1962-), male, Yuncheng City, Shanxi Province, Professor. Research areas include physical geography and environmental change. E-mail:yangtb@lzu.edu.cn

Abstract

This paper focuses on revealing the status quo and variation of glaciers in the western region of Tanggula Mountains. The ratio threshold, NIR water identification and visual interpretation were used to extract the boundary of glaciers based on Landsat data (TM/ETM+/OLI) from 1990 to 2015. In particular, the NIR water identification is a new method to extract glaciers from water, which is suitable to improve the traditional method of ratio threshold. This study used spatial interpolation method to evaluate temperature and precipitation changes. The kriging interpolation method was adapted to manipulate and to extract the appropriate data based on ten weather stations. Comparing to the variations and characteristics of glaciers and climate change from 1990 to 2015, we concluded that glacial retreat in the western region of Tanggula Mountains was serious. The glacier area reduced from 1 693.65 km2 to 1 490.81 km2, respectively, in 1990 and 2015, in general, approximately 202.84 km2 (11.98%) of glacier area has been retreated in the last 25 years. Moreover, the rate of glacier decline after 2000 was much faster than the last decade of the 20th century. In addition, the decreased area of glaciers in the lower altitude basins below 5 000 meters occupied 94.84% of the total change area while the glacier above 5 000 meters almost had no change. The kriging interpolation of the meteorological data indicated that the southeast of the study area was damp and hot while the northwest was cold and dry. The characteristic of temperature distribution from the northwest to the southeast presented from low to high, and precipitation increased in the first of the study period and then decreased but both of them were not very significant. In short, the temperature of study area was increased more prominently since 2000, while the precipitation change was very weak. The mean annual temperature and precipitation of 1980-1989a, 1990-1999a, and 2000-2013a were -3.53 ℃, -3.20 ℃, -2.22 ℃, and 384.49 mm, 354.27 mm, 428.13 mm, respectively. The study found that the glacier change was consistent with temperature variation in spite of the adverse effects of increased precipitation. Therefore, the research concluded that the precipitation change was not more significant comparing to temperature change. In other words, the main reason of the rapid decrease of glaciers in study area was likely due to the rise of temperature.

Keyword: Glacier retreat; The western region of Tanggula Mountains; NIR water identification; Kriging interpolation; Climate change.
1 引言

2 数据与方法
2.1 数据来源

2.2 冰川解译方法

 Figure Option 图1 “ 比值阈值-NIR水体识别法” 冰川提取及NIR统计直方图第一行是使用常规比值阈值法从3幅遥感数据(TM/ETM+/OLI)中提取的冰川初始边界, 第二行是对应的3幅遥感数据近红外波段的地物统计分布直方图, 第三行是使用比值阈值法与NIR水体识别相结合的方法从上面对应的3幅遥感数据中提取的冰川初始边界Fig.1 Glaciers extraction based on “ the ratio threshold-NIR water identification method” and NIR histogramThe data in the first row are initial glacier boundaries from three remote sensing images which used the common ratio threshold. The second are statistical histograms of NIR from the three images. The third are glacier boundaries from the three remote sensing images based on “ the ratio threshold-NIR water identification method”

2.3 气候变化研究方法

2.4 误差分析

$φ=|P-Q|P×100%$(1)

3 结果与分析
3.1 冰川变化概况

 Figure Option 图2 研究区冰川分布图国界和行政界线数据来源于国家基础地理信息系统Fig.2 The distribution and samples of the glacier in study regionThe data of national boundary and administrative boundary coming from National Geomatics Center of China

3.2 不同海拔区间和不同坡向冰川的变化

 Figure Option 图3 不同海拔区间内冰川面积分布图Fig.3 The distribution of glaciers in different elevation grade

 Figure Option 图4 不同坡向冰川分布图Fig.4 The distribution of glaciers from different aspects

3.3 气候变化

 Figure Option 图5 不同阶段平均气温和降水对比变化插值图Fig.5 The variation of mean annual temperature and precipitation from different period

4 讨 论
4.1 冰川变化与气候变化的关系

4.2 其他学者对唐古拉山冰川的研究对比

5 结 论

(1) 唐古拉山西段冰川总体退缩较严重, 1990— 2015年冰川面积由1 693.65 km2退缩到1 490.81 km2, 退缩了202.84 km2, 占1990年冰川面积的11.98%; 近25年有25条冰川完全消失。

(2) 研究区冰川退缩主要发生在海拔5 800 m以下地区, 约占总退缩面积的94.84%; 可能受水汽来源的影响研究区东北、东、北朝向的冰川相比于其他朝向退缩更严重, 退缩幅度更大。

(3) 空间插值分析表明研究区东南部相对较湿热而西北部干冷, 西北— 东南方向温度分布呈现由低到高的变化趋势, 区域整体气温普遍上升, 尤其是2000年以来升温更加显著。插值变化显示增温区从研究区中心向周围辐射, 高增温区几乎已经覆盖整个冰川区域; 而降水量先减少后增加, 整体变化幅度不大。

(4) 唐古拉山西段冰川的加速退缩主要是由升温造成的。

The authors have declared that no competing interests exist.