Research On The Dynamic Changes And Driving Factors Of The Glacier-fed Lakes In Typical Global Areas

Glaciers and lakes are indicators of climate change and have profound impacts on climate change.Studying the dynamic changes of glacial-fed lakes has important theoretical and practical significance for revealing the global climate change law and forecasting climate change.Due to factors such as terrain and climate,the conventional technologies are difficult to dynamically monitor glacial-fed lakes.Therefore,using the Landsat TM/ETM+/OLI remote sensing image data from 1995,2005,and 2015,this paper comprehensively uses "3S" technology and statistical analysis methods based on the extraction of glacial-fed lakes.First the global glacial-fed lakes area,quantity and their changes in the three periods are researched;Then selected Ten typical glacial-fed lakes around the world were selected to analyze the seasonal variation of lakes.Finally taking Tibetan Plateau a for instance,the research analyzes the driving factors of lakes change in the Tibetan Plateau during recent 20 years.The results show that:(1)The use of water body index combined with DEM data to extract glacial-fed lakes can effectively remove the effects of mountain shadows on glacial lakes in high altitude and latitudes.It is verified by Google Earth and 600 Verification points that the total extraction accuracy reaches 96%,which demonstrates the method more suitable for glaciers-fed lakes extraction.Through the selection of end elements,the BP neural network method is used to classify the Tibetan Plateau glaciers and other land features,and overlies multi-temporal images.The classification results can distinguish water bodies,glaciers,soil and other objects,and effectively remove disturbances of snow to glaciers.Compared with the results of the second glacier catalogue,the area error is 0.09.(2)The glacial-fed lakes in the study area in the three periods from 1995~2015 showed an overall expansion trend,but the glacial-fed lakes varied from continent to continent,Asian glacial-fed lakes showed a substantial expansion trend,with an area growth rate of 7.8% and a quantity growth rate of 4.7%.Glacier-fed lakes in North America increased at a steady rate,with an area growth rate of 0.6%.The area and number of lakes in Europe and South America increased unsteadily,their area growth rates increased by 1.7% and 4.1%,respectively,and the number growth rates were 7.4% and 11.3%,respectively.Oceania's lakes area decreased by 1.4% unsteadily,and the number has been increasing by 20.6%.Glacier-fed lakes in Africa have retreated extensively,with an area growth rate of-20.2% and the number of lakes decreasing by 9.5%.The change trend of lakes with different areas and sizes was also different.the proportion of lakes with larger than 100km2 in the total area of lakes was largest,and the change of the total area of lakes was most obvious.The area of lakes with smaller than 1km2 was most,and the number change was most dramatic.The seasonal variation of ten typical Glacier-fed lakes was obvious,the area in summer and autumn expanded,and the area in winter and spring shrinked.(3)The glacier-fed lakes in the Tibetan plateau expanded in the three periods.The lake areas in 1995,2005 and 2015 were 10700.5 km2,11910.7 km2 and 12518.3 km2,respectively.Compared with 1995,the number of lake increased by 2041 in 2005,and by 21 lakes in 2015.Spatial variation of glacier-fed lakes area differed obviously among basins in study area.The lake area in the Qiangtang plateau expanded greatly,and the lake area in the Qaidam Basin expanded tardily.The lake areas in Brahmaputra River Basin is relatively stable.The number and area of lakes showed a tendency of increasing first and then decreasing with increase of altitude.The increase of temperature and glacial retreat was the main reason for the change of glacial-fed lakes area and quantity in the Tibetan Plateau during the period.Topographic factors were also one of the factors that affected lake changes.