基于偏移追踪的青藏高原卓琼冰川流速监测及成因分析

Monitoring ice velocity by SAR offset-tracking and analysis of influence factors for the Kangshung glacier in the Tibetan plateau

冰川作为地球系统中重要的组成部分,是全球气候变化的敏感指示器和调节器.冰川运动的遥感监测也是进行冰川研究的重要内容.本文主要采用偏移追踪的方法,利用2003-2010年期间7对雷达单视复数数据监测了青藏高原珠穆朗玛峰地区的卓琼冰川运动情况.经验证,本研究获得的冰川流速结果可靠.卓琼冰川的流向自西向东,流速自冰川末端向上游积累区逐渐增加,流速大小主要来自距离向的贡献.研究结果显示,卓琼冰川在2003-2005年期间流速较大,最大流速达到45 m·a^(-1),而在2005-2010年期间流速有所降低,最大流速在35~40 m·a^(-1)范围内波动;卓琼冰川年际间流速变化基本一致,冰川中部存在流速突变情况,突变幅度为3~7 m·a^(-1),但该尺度的突变并不会影响卓琼冰川的总体运动趋势.此外,本文还分析了气象以及地理位置因素对卓琼冰川运动的影响.

As an important component of the earth system, glaciers are sensitive to global warming which can result in glacier retreat. This feedback acts more on mountain glaciers than Antarctic or Arctic glaciers. To quantify the role of glaciers in climate change, it is essential to keep tracking glacier motion, especially glacier velocity, which will pose impact on the mass balance of glaciers and the surrounding environment. The development of remote sensing instruments overcomes the deficiency of field monitoring technology in the past and contribute to glacier monitoring, especially the Synthetic Aperture Radar （SAR） with all-weather and day-and-night imaging capabilities. In this study, we use the SAR offset-tracking method to estimate ice velocity of the Kangshung glacier, one of the active glaciers in the Khumbu basin of the Tibetan plateau, based on seven couples of Single-Look Complex （SLC） data from 2003 to 2010. Compared with D-InSAR, SAR offset-tracking can obtain more information from both range and azimuth displacement. The ice velocity obtained in this work is proved to be reliable through validation with previous research. The results show that the Kangshung glacier flows from west to east and the ice velocity gradually increases from the terminus to the upstream. The contribution of ice velocity mainly comes from the range direction. In the early years from 2003 to 2005, the ice velocity was much higher with maximum up to 45 m·a-1. In the late years from 2005—2010, the ice velocity decreased slightly and the maximum fluctuated between 35 m·a-1 to 40 m·a-1. However, the annual velocity change of Kangshung glacier was stable in the study period. Although there existed fluctuation of 3 m·a-1 to 7 m·a-1, it did not affect the general trend of glacier movement. Besides, we also analyzed the impacts of meteorological environment and location on the motion of the Kangshung glacier.