| Glaciers,as an important part of freshwater resources,are very sensitive to climate change.Glacier surge is not only a basic process of glacier dynamics,but also an important parameter.The study of glacier surge can provide basic supporting data for efficient utilization of glacier resources and prediction of glacier change.In recent years,under the background of global warming,most glaciers are retreating,but some of the glaciers in the Karakoram Mountains show abnormal behavior such as advancing or moving,which has attracted the attention of many scholars at home and abroad and is called the"Karakoram Anomaly".Glacier prance refers to the phenomenon that glaciers periodically move rapidly in a relatively short period of time.It is of great significance to prevent secondary disasters caused by surging glacier and to promote the research progress of glacier surge.The main research contents and conclusions of this paper are as follows:(1)Identification of glacier surge in the Karakoram MountainsBased on the Randolph Glacier Inventory(RGI 6.0),the reported active glaciers were extracted,and their characteristics were summarized and cataloged.To identify surging glaciers(including similar surging glaciers)based on remote sensing technology in the 1970s to the present and add them to the above catalog;In this paper,a total of 8 surging glaciers were added,and the starting and stopping time,peak velocity and other information of the surging glaciers were determined according to the spectral data of the glacier surge velocity.Based on the data of Hexagon and ITS_LIVE,it is found that the Urdak Glacier had a spring surge during 1991-1998,and the ice velocity of the Sax Dry Glacier was obviously too fast in 1991,with a maximum value of 187m a-1.The ice velocity of the Sax Dry Glacier showed a stable trend in 1995.After a 3-year stable period,the glacier velocity increased again,and reached the peak value again in 2006(141 m a-1),and slowed down to a stable trend in 2012.(2)Comparison of temporal and spatial differences of surging glaciersBased on the above cataloged data,the spatial distribution characteristics of the number and size of the surging glaciers in the eastern,western and central Karakoram regions were compared.The results showed that the western and central Karakoram regions(53)and the eastern Karakoram region(54)had the most surging glaciers,while the eastern Karakoram region had 36.The most surge glaciers are larger than 50 km2 in the west of Karakoram,and the most widely distributed in the northeast direction.By comparing the characteristics of glacier surge in different seasons,it is found that the glacier velocity shows three kinds of conditions.First,it has a strong seasonal control.The velocity of the glacier in winter and summer is significantly different.It is observed that the velocity of the glacier in summer is generally greater than that in winter.Second,there are many glaciers in the study area that maintain relatively high flow rates in both winter and summer.Third,different parts of a glacier may respond differently to seasonal changes.By comparing the occurrence frequency of surging glaciers in different time periods,it is found that the occurrence frequency of surging glaciers is higher after 1990,which may be related to the development of remote sensing technology.(3)A comparative study of surge glaciers and normal glaciersThe differences in glacier velocity,geometry,topography,and the number of glaciers in different sizes were compared between the surge glaciers and the normal glaciers.It is found that the elevation difference of the surging glacier is significant,the slope is steep,the slope is southward and the area is large.By quantifying the variation characteristics of glacier velocity and elevation between the surging glacier and its adjacent normally-advancing glacier at the glacier scale,it is found that the glacier velocity of the surging glacier has an obvious abrupt change during the acceleration process,while the ice velocity of the normally-advancing glacier has no obvious abrupt change.The surface elevation of the surging glacier is different from that of the normal advancing glacier.The vertical profile of the surging glacier has an obvious sag and uplift,while the normal advancing glacier only presents uplift at the end of the glacier.(4)Causes of glacier surgeIn this paper,the characteristics of climate change in Karakoram Mountains are extracted and analyzed.The increase of temperature and precipitation plays an important role in the development of surging glaciers.From 1950 to 2019,the overall temperature in the Karakoram Mountains showed an upward trend,and the precipitation was relatively stable in the southwest,while slightly increased or tended to be stable in the northeast.During 1950-1979,the distribution of temperature and precipitation in the Karakoram Mountains was similar to that in 1950-2019.The temperature increased slightly,but the precipitation in the northwestern part of the Karakoram Mountains increased more than that in the southeastern part.During 1980-2019,the annual mean temperature increase rate in Karakoram Mountains was significantly higher than that in 1950-1979,while the precipitation showed an obvious decreasing trend.Finally,the role of hydrological transition model and thermodynamic mechanism model in the Karakoram glacier surge is discussed.Figure[41]table[8]reference[121]... |
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