Remote Sensing Monitoring Of Glacier Changes Between Eastern Pamirs Plateau And Western Kunlun Mountains From 1976 To 2016

The Eastern Pamirs Plateau belongs to the Hercynian fold belt in geological structure,the same as the Western Kunlun Mountains.The mountains are majestic and magnificent as the whole,standing on the northwest edge of the Tibetan Plateau.Moreover,in terms of climate,the Eastern Pamirs Plateau and the Western Kunlun Mountains are also affected by westly circulation and south Asia monsoon.Therefore,two geographical units all belong to the same alpine dry zone under the aspect of climate that is why the paper studies the Eastern Pamirs Plateau and the Western Kunlun Mountains in the same research area.The domestic glacier research focus on Western Kunlun Mountains,and analyzes the glacier surface movement velocity.The study time series was short,and there were few studies on the evolution of the Eastern Pamirs Plateau and Western Kunlun Mountains glacier in eastern China.However,most foreign articles on glacier changes focused on the entire Tibetan Plateau.In this study,we can find that there are few reports on glacier changes in the world glacier journal.The innovation of this paper is to study the glacier changes in the Eastern Pamirs Plateau and Western Kunlun Mountains as a whole,and to make a detailed comparative analysis of glacier changes of the two geographical units in the 40 years.In addition,the surface movement velocity of Yulong Glacier is estimated in this paper.In this study,the MSS,TM,ETM+,and OLI Landsat images were applied to extracted glacier boundaries of the Eastern Pamirs Plateau and Western Kunlun Mountains,in the northwestern edge of the Tibetan plateau,(1976,1996,2006,and 2016).This paper adopted different image processing methods with each other,because of the MSS and others images quality are different.Firstly,we extracted the glacier boundaries using the visual interpretation method in 1976.Secondly,according to the images of MSS,TM,ETM+ and OLI,the glacier boundaries were extracted automatically by the band ratio method.In different image periods,the band ratio threshold is not fixed,so it is necessary to try several times and find the most reasonable band ratio threshold.In this study area,we believe that the band ratio threshold from 1.8 to 2.0 is the most accurate.On this basis,we modified the classification results combined with Google Earth and glacier interpretation.Finally,the glacier boundaries of the Eastern Pamirs Plateau and Western Kunlun Mountains(1976,1996,2006,and 2016)is obtained,and the characteristics of glacier change is analyzed in depth from 1976 to 2016.At the same time,according to the temperature and precipitation data recorded by the meteorological observation station around the research area,the climate change of the research area from 1960 to 2015 was analyzed.On this basis,the response of glacier to climate is discussed in depth.The main conclusions are as follows:? Glacier changes: the total area of glacier has been decreased from 1976(9482.90km2)to 2016(8327.29km2),with a shrinkage ratio of 12.19%,and the annual rate of retreat was 0.30% · a-1.In three time phases:1976~1996,1996~2006 and 2006~2016,the glacier retreat was "fast-faster-slower".The glacier retreat rate was larger in the second stage than that of the first and the third stages,and the slowest retreat rate was observed in the third stage.The trend of glacier changes in the Eastern Pamirs Plateau is consistent with the research area,where the fastest retreat rate of glacier is recorded in the Kungai Mountains.While the variation of glacier in different districts of the Western Kunlun Mountains is very significant.Overall,the slowest glacial retreat rate was recorded in the central Kunlun peak area and the glacier retreat rate was faster in both ends.Smaller glaciers appeared to shrink faster than larger glaciers,and more sensitive to climate change.The distribution of glaciers at different altitudes in this study is concentrated approximately from 4900 m ~ 6400 m,while the retreat rate of the glacier was greater at a lower elevation than that of at higher areas.However,the glacier changes distributed below 4900 m are more volatile.Over the past 40 years,the glacier retreat rate in the study area was faster than the surrounding area.? Climate changes: Between 1960 and 2015,the annual average temperature rose obviously,with an overall increase of 1.65?,and the average rate of warming up is 0.3?/10 a.It is obvious that the average summer temperature and the winter mean temperature are both showed a warming trend,and the winter average temperature is more significant than that of the summer.However,the annual precipitation increased slightly with a slow increase.Therefore,this phenomenon greatly weakened for the glacier accumulation efficiency of the winter glacier supply in the study area.It can be concluded that the glacier retreat between the Eastern Pamirs Plateau and the Western Kunlun Mountains is caused by a significant increase in temperature,and the slow increase in annual precipitation is insufficient to compensate for the loss of material in the glacier.? The NCC algorithm is used to calculate the surface movement velocity of Yulong Glacier for three time phases:1996 ~ 1997,2007 ~ 2008 and 2015 ~ 2016.In the spatial distribution,the maximal and high value distributions are most concentrated near the equilibrium line.In addition,the speed of the surface movement decreases along with the reduction of altitudes;In the interannual changes,the surface movement speed of glacier was very fast from 2007 to 2008.