东帕米尔高原昆盖山跃动冰川遥感监测研究

Monitoring a glacier surge in the Kungey Mountain, eastern Pamir Plateau using remote sensing

冰川跃动是冰川周期性地快速运动,给下游生命财产安全带来巨大威胁。对已经发现的跃动冰川进行监测不仅有助于提高对冰川跃动机理的认识,而且对冰川跃动灾害预警预报和风险评估都具有重要的意义。在中国第二次冰川编目中发现,1963-2009年东帕米尔高原昆盖山的5Y663L0023冰川末端发生大幅前进。本文利用Landsat影像、ASTER立体像对等数据对该冰川前进过程进行监测研究。结果表明:该冰川于1990-1992年和2007-2013年分别前进81±30 m和811±30 m,其中2007-2013年的前进属于跃动引发的前进。其中跃动最高峰在2007年8月21日-2008年10月26日,期间32.7×10~6m^3的冰体发生卸载,导致末端前进了704±30 m,面积扩张了0.34 km^2。针对东帕米尔地区跃动冰川周期研究的空白,本文认为该冰川跃动周期中跃动期为4 a,平静期最短为15 a左右。该冰川属于多温型冰川,跃动受热力学机制影响的可能性较大,但液态降水、冰雪融水的增加也是影响因素。

Surge-type glaciers are characterized by rapid ice movement in a relatively short phase and mass redistribution after a comparatively long quiescent phase. They are also related to glacier hazard events such as glacier collapse, flood, and landslide that may cause massive losses to humans. Therefore, monitoring surged glacier will not only help us to explore the mechanism of glacier surge, but also further the research in glacier disaster early warning and risk assessment that have important practical significance. In the process of compiling the second Chinese glacier inventory, a glacier coded as 5 Y663 L0023 in the Kungey Mountain, eastern Pamir Plateau was found to have advanced a long distance during 1963-2009. Thus, the main aim of this study was to investigate this advanced glacier based on ASTER and Landsat data. From 1990 to 1992, the glacier advanced about 81 ± 30 m. Then the glacier continually advanced about 811 ± 30 m during 2007-2011, which may be attributed to surge. The surge initiation and termination took place from 5 August 2007 to 2011. A total volume of glacier ice of about 32.7×106 m^3 was transferred from the upstream below the equilibrium line of the glacier in the main phase of surging between 21 August 2007 and 26 October 2008. This led to an increase of the glacier surface maximum thickness(128.17±0.17 m), glacier area(0.34±0.03 km^2), and glacier length(704±30 m). To fill the gap in glacier surge period research, we suggest the active phase of the surged glacier was 4 year, the quench phase was likely about 15 years at least. The main reason behind the glacier surge may be the increase in mean annual air temperature and annual precipitation, as was recorded at the Tashkurgan Meteorological Station in recent years. On the one hand, ice and snow meltwater and liquid precipitation were carried through the crevasses from the surface of the glacier down to the glacier bed when temperature rises. Consequently, the high shear stresses along the frozen side walls due to high-pressure water dammed at the bed progressively broke the ice until glacier surge. On the other hand, build-up of ice from snowfall, avalanches, and snowdrift in the reservoir area increased the driving stress, which led to higher ice creep rates. Eventually, part of the glacier bed was raised to the pressure melting point and produced meltwater. The meltwater did not escape from the glacier and raised basal water pressure that led to reduced basal drag and faster sliding.