基于地形指数的格陵兰冰面水系建模与评价

During the annual ablation period, meltwater on the ice surface is transported to the edge of the ice sheet through the ice surface water system, resulting in the mass loss of the Greenland Ice Sheet. The dynamic changes of the ice surface water system determine the mode and efficiency of meltwater transport on the ice surface and significantly affect the mass balance of the Greenland Ice Sheet. As one of the key factors determining the dynamic changes of the ice surface water system, the degree to which the ice surface topography controls the dynamic changes of the ice surface water system remains to be studied. In this study, a typical area (~1800 km²) in the southwest of the Greenland Ice Sheet was selected as the study area, and the ArcticDEM with a spatial resolution of 32 m was used as the experimental data. Two topographic indices, the Topographic Wetness Index (TWI) and the Height Above the Nearest Drainage (HAND), were used to simulate the distribution of the ice surface water system. Combined with 29 Sentinel - 2 images with a spatial resolution of 10 m and 30 Landsat - 8 images with a spatial resolution of 30 m during the ablation period from 2016 to 2019 to extract the ice surface water system as verification data, the accuracy of the topographic index in modeling the ice surface water system was revealed through fuzzy comparison. The research results show that: the topographic index can better model the distribution of the ice surface water system (overall accuracy > 72%), the distribution of the ice surface water system is mainly controlled by topographic factors, and the introduction of the topographic index into the study of ice surface hydrology is helpful to enhance the understanding of the ice surface hydrological process.

每年消融期,冰面融水通过冰面水系输送至冰盖边缘,造成格陵兰冰盖物质损失。冰面水系的动态变化决定了冰面融水输送的方式与效率,显著影响格陵兰冰盖物质平衡。作为决定冰面水系动态变化的关键因素之一,冰面地形对冰面水系动态变化的控制程度有待研究。本研究选取格陵兰冰盖西南部典型区域(~1800 km~2)作为研究区,以32 m空间分辨率ArcticDEM作为实验数据,利用地形湿度指数(Topographic Wetness Index, TWI)和最邻近河网高差指数(Height Above the Nearest Drainage, HAND)两种地形指数模拟冰面水系分布,结合2016-2019年消融期29景10 m空间分辨率Sentinel-2和30 m空间分辨率Landsat-8影像提取冰面水系作为验证数据,通过模糊比较揭示了地形指数建模冰面水系的精度。研究结果表明:地形指数能够较好地建模冰面水系分布(总体精度>72%),冰面水系分布主要受地形因素控制,将地形指数引入冰面水文的研究,有助于加强对于冰面水文过程的理解。