The Research Of Glacier Variation And Climate Changein Eastern Tianshan(1990-2011)

In the scene of global warming,the glaciers of the eastern Tianshan is the most sensitive to climate change.This paper selected the eastern of Tianshan(Bogda Mountain,Balikun Mountain,Harlik Mountain) as the study and utilized Landsat series satellites remote sensing images of1990,2001and2011as the source of data.In the support of Geography Information System,we extracted the glacier outlines using the band ratios and supervised classification,with some necessary manual editing to correct the glacier outlines and then got the information including area,different sizes,aspect and so on.Based on the seven meteorological stations data(Tsai lake,Urumqi,daban,Qitai,Balikun,Hami andYiwu) of average annual precipitation,annual mean temperature,summer mean temperature and winter average precipitation during1975-2011,using linear fitting and average contrast methods,we analyzed the characteries of climate change in the study region,and then discussed the relationship between glacier change and climate change.On the basis of analyzing,we made the preliminary forecast for glacier area changes in future. The paper also made the comparative analysis about area change in eastern Tianshan and others in the west.The main results are as follows:(1)Glacier Change:The area of eastern Tianshan was368.06km2、312.78km2and269.43km2from1990to2011,respectively.The area of glaciers presented shrinking trend in our study region and decreased98.63km2,accounting for26.80%(4.48km2/a)of the glacier area in1990.The large scale of glaciers was retreating with the process of broking down into the median size of glaciers and then its continued to break down into the small glaciers,resulting the area and count of small glaciers increased. We extracted the information of glacier area in different elevations,and analyzed the change of area at3300-5000m.Results indicated glaciers retreat rate decreased with increasing altitude and was fastest at3300-3400.We also extracted the information of different aspect,the result showed the retreat rate in the southeast slope was the fastest,reaching30.68%,and then was the western,northwest and east slope,reached28.77%、29.15%and29.32%,respectively. Glacier retreat rate was slowest in the southern slope for25.24%.Finally,we extracted the area of Bogda Mountain,Balikun Mountain,Harlik Mountain and the change rates of area were33.58%、25.67%and16.08%,respectively.The results showed the retreat rates of the those glaciers were gradually decreased.(2)Climate Change:Annual mean temperature experienced upward trend in general from1975-2011and the linear regression coefficients was higher.The linear fitting warming reates are0.04℃/a、0.03℃/a、0.01℃/a、0.05℃/a、0.03℃/a、0.09℃/a and0.02℃/a,respectively.The average annual precipitation trend show slight increases and the linear fitting warming reates are0.98mm/a、0.53mm/a、1.02mm/a、1.35mm/a、0.02mm/a、0.88mm/a、0.39mm/a,respectively.We also found the summer temperature showed the continued warming trend.(3)The relationship between glaciers and climate change.The retreat of glaciers was mainly caused by increased temperature in the east of Tianshan.We also found there was a lag about10years in glacier response and climate change.Therefore,we think the future glacier maybe continue to retreat.The paper results also showed there is a lag time about10years in glacier response and climate change in Bogda Mountain,Balikun Mountain and Harlik Mountain.The other hand,the size of the valley glacier retreat rate was the result of the scale,thickness and the location of glacier.(4)Constract of glacier change:The glaciers change in the eastern of Tianshan is consistent with the west of China,but the retreat rate was fastest in the eastern of Tianshan and then was the west,and the south was smallest.