Lake Area Change And Its Response To Climate Change In QiangTang Plateau

The Qiangtang Plateau is located in the hinterland of the Qinghai-Tibet Plateau.There are many lakes in this area,which play an important role in the natural water cycle and water balance.Under the background of global climate change,the temperature of the Qinghai-Tibet Plateau has increased significantly.The changes of lakes on the Qiangtang Plateau contain important information on the plateau climate.The changes of lakes in this region have been highly valued by scholars in the fields of meteorology,hydrology and ecology.Taking the Qiangtang Plateau as the research area,this paper uses remote sensing and geographic information system technology to extract water bodies from the Landsat satellite remote sensing image data in four periods of1990,2000,2010 and 2020,and uses linear regression combined with meteorological data.,Mortlet wavelet period and MK mutation test method to analyze the change characteristics of lake area and climatic factors,and use Pearson correlation analysis method to discuss the evolution law of Qiangtang Plateau lake group in the past 30 years and its response to climate change.The specific research results as follows:(1)Comparison and confirmation of water extraction methodsAccording to the characteristics of rich lake types,typical plateau climate,and abundant glaciers,this paper selects the image of strip No.141/36 located in the interior of the Qiangtang Plateau as the experimental sample area.The maximum likelihood method has the best extraction effect,with an overall classification accuracy of 98.26%and a Kappa coefficient of 0.96.Therefore,this paper uses the maximum likelihood method to extract water bodies in the entire area of the Qiangtang Plateau.(2)Changes of lake area in the Qiangtang Plateau in the past 30 yearsIn 1990,2000,2010 and 2020,the area of lakes in the Qiangtang Plateau was26543.2km2,29179.4km2,33158.7 km2,and 36439.6km2 respectively,showing a change from rapid growth to slow growth.The lake area increased in total.The lake area increased to 9896.4km2,accounting for 27.16% of the total area,of which the lake area increased the most during 2000-2010(3979.2km2),followed by 1990-2000(3280.9km2),and the least in 2010-2020(2636.2 km2).From the perspective of the spatial distribution of area changes,growing lakes are distributed in various regions of the Qiangtang Plateau,while shrinking and disappearing lakes are mainly concentrated in the southeastern and southern regions of the Qiangtang Plateau.There are few stable lakes,mainly in the central area of the Qiangtang Plateau.Among them,440 lakes were newly added or expanded,accounting for 78% of the total number of lakes,while only90 lakes were disappeared or shrunk,accounting for 16% of the total number of lakes.The total area of expansion(9130.9km2)was much larger than that of shrinkage(1351.5km2).(3)Characteristics of climate change in the Qiangtang Plateau in the past 30 yearsIn the past 30 years,the climate of the Qiangtang Plateau changed from warm and humid to warm and dry.The annual average temperature and precipitation increased significantly in 2003 and 1999 respectively(P<0.05),the temperature increase rate was0.5?/10 a,and the precipitation increase rate was 20.1mm/10a;the annual average relative humidity In 2007,there was a significant abrupt decrease,with a decreasing rate of 2.3%/10a;the snow cover continued to decrease without abrupt change.In addition,the annual mean temperature,precipitation and relative humidity all have oscillation periods of 2-4 years,but there is no oscillation period for snow depth.(4)The relationship between lake area and climate change in the Qiangtang Plateau in the past 30 yearsThe increase of lake area in the Qiangtang Plateau was related to the increase of temperature in the past 30 years and the increase of relative humidity from 1990 to 2006(P<0.01),but the correlation with precipitation was not significant(P>0.05).Among them,the temperature that has the greatest impact on the entire Qiangtang Plateau is the temperature.The increase in temperature causes the snow depth to drop significantly,which leads to the continuous expansion of the lake area caused by the melting water of glaciers and permafrost.(5)Column analysis of typical lakesIn the past 30 years,the lake areas of Selin Co and Nam Co have increased by650.70km2 and 76.94km2,respectively.There are obvious spatial differences between the lakes of Selin Co.The lakes face south and northward.to the greatest extent.Both lakes have extremely significant correlations with the increase of air temperature in the basin and the decrease of snow depth in the cold season(P<0.001),while the correlation with relative humidity and precipitation is not significant(P>0.05).Therefore,the temperature In particular,the significant increase in temperature in the cold season caused the increase of ice and snow melt water in the upper reaches of Selin Co and Nam Co,which is the main reason for the increase of the lake surface area.