Comparison Of Glacier Volume Results Based On The Different Methods

As an important component of the cryosphere,glaciers are natural“recorders”and“warning devices”that reflect climate change and are also important freshwater resources.Under the background of global warming,glaciers in western China are generally shrinking and thinning.Especially for the arid regions of the northwest,glacialmeltwater is the most important water resources.Monitoring glacier changes at the basin scale,especially the changes in glacier ice reserves,has important practical and theoretical implications for a comprehensive understanding of the impacts of glacial changes on water resources.Meanwhile,glacier ice reserves,as one of the important parameters of glaciers,are not only important parameters for constructing glacier hydrology,dynamics and disaster models,but also significant indicators for assessing the impact of glacier changes on river runoff and developing active measures for disaster prevention and mitigation.Its vital premise for contributing to see level rise This paper is based on China's first and second glacial catalogue data and Landsat OLI remote sensing imagery to analyse glacial area changes in the Laohugou Basin from 1960s to 2017 by using multi-source DEM data;Secondly,in order to accurately assess the total amount of glacial resources and its changes we compared and analyzed the advantages and disanvantages of different glacial ice storage estimation methods,which provides a reference for the research on the status quo and variation law of glacial water resources and the contribution of glacial change to sea level rise.Research indicates:(1)In 2017,there were 101 glaciers in the Laohugou Basin with an area of 76.18 km~2.Among them,Most glaciers range in size from 0.1~0.5 km~2.However,the total area of glaciers with an area of 20~50 km~2 is the largest due to the large area of a single glacier.In the past 60 years,the number of glaciers in the Laohugou Basin has decreased by only one,but the area of glaciers has decreased by 18.58 km~2(-0.33 km~2/a).From the perspective of different scale changes,the number and area of glaciers with an area<0.1 km~2 increased,and the number of glaciers with an area between 2~5 km~2and 20~50 km~2remained unchanged.The number and area of other scales were reduce the trend.From the elevation point of view,the altitude above 4800 m is the main area of glacial retreat,and the glaciers below 4100 m and above 5400 m have completely disappeared.From 1960s to 2017,the number and area of glaciers in all directions of t the Laohugou Basin showed a decreasing trend.The rapid increase in temperature and the slow increase in annual precipitation are the root causes of the retreat of glaciers in the region.(2)The empirical formula method has great limitations in calculating the ice volume of specific glaciers,but it is ideal in regional scales.Although the results of the empirical formula method for different glacial ice reserves in the same area are relatively similar,there are also significant differences.However,based on the simplicity and efficiency of its calculation method,the conversion coefficient and the range of glacial area change are relatively narrow,and the difference between the same types of glaciers is small,it is widely used in glacial cataloging work and regional scale glacial change research.(3)Compared with the measured glacier thickness,the empirical formula method estimates the ice thickness error to be 42.38%,and the model simulation ice thickness error is-18.89%.Therefore,applying the ice thickness empirical formula method to the calculation of specific glacier ice reserve without correction will cause a large error;The model estimation method is mainly based on the developmental condition of glaciers and their material balance changes.Although it is suitable for the calculation of specific glacial ice reserves,in different mountain ranges and watersheds,due to the obvious differences in glacier topography,climate,glacier structure,etc.,the characteristics parameters are difficult to determine and have greater limitations.Even so,the glacial thickness empirical formula method and the model simulation of the ice thickness method are still helpful to studying the thickness of the non-measured glaciers.Moreover,the model simulation method is closer to the true value and provides a powerful tool for estimating the thickness of different parts of the glacier.(4)With the rapid development of remote sensing technology,geodetic method based on multi-source remote sensing data has become one of the most important methods for studying relative changes in glacier ice reserves.Although there are many uncertain factors,with the advancement of remote sensing technology,theestimation accuracy of this method is also increasing,which has attracted more and more scholars'attention..Compared with the model simulation method and the empirical formula method,the geodetic method is more suitable for the relative change of glacier ice reserves at the regional scale.