Measuring Ice Flow Velocity on the Greenland Ice Sheet Using Stable Supraglacial River

The ice flow velocities of many outlet glaciers on the Greenland Ice Sheet (GrIS) have increased dramatically over the past two decades, leading to significant GrIS mass loss. It is challenging to match multitemporal synthetic aperture radar or optical images because the GrIS ice surface changes dramatically, particularly during melt seasons. Therefore, ice surface features used for image matching are required to remain persistent even if the other image characteristics change significantly. This letter proposes that supraglacial rivers can be used to match multitemporal images’ tie points (TPs) and to measure the ice flow velocities. First, multitemporal 10-m Sentinel-2 images are used to detect supraglacial rivers by integrating cross-sectional and longitudinal channel information. Second, potential river TPs are created using GIS buffer and overlaying operations. Third, a nonrigid coherent point drift algorithm is used to match river TPs, and the spatial displacements among the corresponding matching river TPs are used to calculate the ice flow velocities. A typical outlet glacier of the northeast GrIS is selected as the study area and six multispectral Sentinel-2 images are used to calculate the summer and annual ice flow velocities during 2016–2018. The results show that the summer ice flow velocity is ~ 640–665 m/a, 9%–14% higher than the annual ice flow velocity (~ 581–588 m/a). The summer and annual ice flow velocities both decrease along the ice and river flow direction. The derived ice flow velocities are closely correlated with two state-of-the-art ice flow velocity products (R
²
≥ 0.981), indicating the high accuracy of the proposed method.