Abstract:

During the annual ablation period, a large amount of meltwater is transported to the margin of the Greenland ice sheet through supraglacial river networks, causing mass loss from the Greenland ice sheet. The dynamics of supraglacial river networks determine the flowpath and efficiency of meltwater routing, and significantly affect the mass balance of the Greenland ice sheet. As one of the key factors that determines the dynamics of supraglacial river networks, the control of the ice surface topography on the supraglacial river network’s dynamics remain unknown. In this study, we modeled the distribution of supraglacial river networks on a typical melting region of the southwest Greenland ice sheet (approximately 1800 km²) using the Topographic Wetness Index and the Height Above the Nearest Drainage method derived from the 32 m Arctic DEM. The modeling results were validated and compared with the frequency observations compiled from 29 scenes acquired from Sentinel-2 imagery at 10-m resolution and Landsat-8 imagery at 30-m resolution. The results show that the Topographic Wetness Index (TWI) and Height Above the Nearest Drainage (HAND) method can be used to model the spatial distribution of the Greenland ice sheet supraglacial river network with an overall accuracy greater than 72%; therefore, the spatial distribution of the supraglacial river network is mainly controlled by the ice surface topography. As shown here, applying topographic indices in the study of supraglacial hydrology can help to improve the understanding of supraglacial hydrological processes.

Key words: supraglacial river network, Topographic Wetness Index, Height Above the Nearest Drainage, Sentinel-2, Landsat-8, Greenland ice sheet