| The Karakoram Mountains is located in the northwest edge of the Tibetan plateau,where there are various modern glaciers.In recent years,the glaciers of the Karakoram Moutains have remained stable and even advanced slightly.It has scientific and social significance to research the distributions and variations of the glaciers and analyze the changes of the ends of galciers in the Karakoram Mountains.Based on Landsat remote sensing images,with the support of the geographic information system platform,the outlines of glaciers in 1978,1991,2001,2015 were extracted by the computer aided classification and visual interpretation methods.The study compared the changes of glaciers at different times,and researched the changes of the glaciers in many aspects,such as size,altitude,direction and slope.Then the study analyzed the basic characteristics of the terminal of surge glaciers in the study area,and discussed the laws of change of the surge glaciers.Finally,the study analyzes the cause of the glacial changes in the study area,using air temperature and precipitation data of meteorological sites that near to the study area,studied the characteristic of climate change in every period of time and discussed glacial changes in response to climate change.In addition,the paper discusses the factors of glacier surging in several aspects.We drawed the following conclusions:The glacier distribution and variation characteristics:1.The glacier area in China Karakoram was gradually decreased from 1978 to 2015,and the average retreat rate of glaciers have showed the trend of fast to slow,especially in 2001-2015.Compared with other parts of the Tibet Plateau,the glaciers of China Karakoram glaciers retreated more slowly.2.The glaciers have retreated on the whole nearly 40 years.However,it is different with other mountain glaciers that some glaciers have remained stable or advanced slightly and even surged.The amount of glaciers is 1106 in the study area,of which 213 glaciers have remained stable and 57 glaciers have advanced and others have retreated.3.The number of small glaciers is the highest,and the area of large-scale glaciers is the largest in the study area.The glaciers have retreated in every size grade.With the increasing of scale,the retreat rate of glacier has shrunk rate decreases.4.The area of glaciers is vary widely in each direction,the glaciers mainly distributed in the northeast and north,and the glacies rarely distributed in the western slope.The retreat rate of glaciers is different in each direction,the retreat rate is bigger in the eastern,southeastern and southern slope,and then,the retreat rate is smaller in the northwest,north and west.5.The glaciers are mainly distributed in the slope of 0° ~ 60°.The glaciers are shrinking trend of each grade level in 1978-2015.The retreat rate of glaciers is the largest in the slope in 35° ~ 40°,and glaciers in other slope is extremely gentle slope or steep region back slower,different slope glacier area shrinking rate line chart of normal distribution of the general form.6.The glaciers in the study area are mainly distributed in the elevation of 4400 ~ 6800 m,the area of glaciers is approximately normally distributed with the change of altitude.The glacier area in each elevation was gradually reduced in 1978-2015,and glacial retreat rate increases with altitude and significantly reduced.The typical glacial movement phenomenon:1.There were 27 terminals of glaciers surged in the study area in 1978-2015,and they happened fast progress in a short time.The movement of glacier terminal mainly concentrated in two periods,1992-1996 and 2004 ~ 2008,the second time living more often than the first time.Overall,the study area from 1990 to 2015 the occurrence of most glaciers have approximate periodic law of normal distribution,frequency of glacier surging have showed a trend of rise.2.The distribution of the terminals of surge glaciers is not uniform in the study area,most terminals distributed in large glacier ice tongue part of the larger scale,the lower part of the altitude,near the river and in the majority with horst koehler qinghe south.The analysis of the causes of glacier change:1.The average temperature and annual precipitation are rise in volatility in each meteorological sites in 1960-2015.We found that there was a good response between the change of glacier area and the change of climate.The increase of precipitation curbed the melting of glaciers in the study area,so the glaciers in China Karakoram shrinked slowly and even growed slightly.2.The glacier surges in China Karakoram mainly rely on the topography of high-altitude,climatic background and glacier morphology.(1)the pressure at the top makes the structure of glacier ice body out of balance;(2)the unstable internal structure of the glacier itself,as well as the internal accumulation of energy change;(3)the glaciers that long length,large area and the highest difference of the top and the bottom elevation are more likely to surge;(4)the glacier mass balance of ice plays an important role,an accumulating snow that is necessary to trigger the glacier movement. |
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