基于延时摄影监测冰川表面运动过程的研究

Monitoring of glacier surface movement by time-lapse photography

延时摄影因可靠、高效和低成本的优势,在冰川监测中应用广泛,特别是对于获取冰川表面连续变化信息而言。本文基于2020年3月—2021年9月物候相机拍摄的梅里雪山明永冰川末端照片及多期无人机影像,利用地面摄影测量技术和互相关算法,提取了日尺度冰川表面运动速度。结果表明:通过物候图像获取的冰川表面运动速度分辨率高,从海拔2 880~3 150 m a. s. l.,冰川总位移介于(129.38±7.76)~(669.95±247.88) m,年均表面运动速度达(79.14±4.74)~(412.86±152.75) m·a-1,呈从中间向两侧减缓的空间分布特征。冰川表面运动速度随季节变化,夏季流速[(0.13±0.06)~(1.99±0.37) m·d-1]快于冬季流速[(0.07±0.06)~(1.35±0.37) m·d-1]。与冬季流速相比,夏季流速受降水和气温升高的影响不稳定。根据流速分离结果,明永冰川末端底部全年处于融化或压融状态,底部滑动对冰川表面运动速度的贡献介于76%~93%。冬季底部滑动占表面流速高达82%,夏季底部滑动对冰川运动起绝对主导作用。本文采用的技术为进一步研究季风海洋型冰川的运动机制提供了参考方案。

Time-lapse photography is widely used in glacier monitoring due to its advantages of reliability,high efficiency and low cost,especially for obtaining continuous change information of glacier surface.Based on the photos of the Mingyong Glacier terminus in Meri Snow Mountain taken by the phenological camera from March 2020 to September 2021 and multi-period UAV images,this study uses ground photogrammetry technology and cross-correlation algorithm to extract the daily glacier surface velocity.The results show that the resolution of gla⁃cier surface motion velocity obtained by phenological images is high.From the altitude of 2880~3150 m a.s.l.,the total displacement of glaciers is(129.38±7.76)to(669.95±247.88)m,and the average annual surface mo⁃tion velocity is(79.14±4.74)to(412.86±152.75)m·a-1,showing a spatial distribution characteristic of slowing down from the middle to both sides.The surface velocity of the glacier varies with the seasons.The velocity in summer[(0.13±0.06)to(1.99±0.37)m·d-1]is faster than that in winter[(0.07±0.06)to(1.35±0.37)m·d-1].Compared with the winter current velocity,the summer current velocity is unstable due to the increase of precipi⁃tation and temperature.According to the results of velocity separation,the bottom of the Mingyong Glacier ter⁃minus is in a state of melting or pressure melting throughout the year,and the contribution of basal sliding to the surface velocity of the glacier is between 76%~93%.The basal sliding accounts for 82%of the surface velocity in winter,and the basal sliding plays an absolutely dominant role in glacier movement in summer.The tech⁃niques used in this study provide a reference for further study of the mechanism of monsoon ocean-type glacier movement.