Cross-Comparison of Albedo Products for Glacier Surfaces Derived from Airborne and Satellite (Sentinel-2 and Landsat 8) Optical Data

• DOI: 10.3390/rs9020110
• Publication Date: 2017-01-27T16:23:02Z
• Authors: Kathrin Naegeli; Alexander Damm; Matthias Huss; Hendrik Wulf; Michael Schaepman; Martin Hoelzle
• Keywords: Sentinel-2; Light-absorbing impurities; Albedo; APEX; glacier; narrow-to-broadband; Landsat; Albedo; glacier; narrow-to-broadband; glacier; Albedo; Light-absorbing impurities; APEX; Sentinel-2; Landsat; narrow-to-broadband; Science; 1900 General Earth and Planetary Sciences; Q; Light-absorbing impurities; 01 natural sciences; 10122 Institute of Geography; 13. Climate action; 910 Geography & travel; Sentinel-2; APEX; Landsat; 0105 earth and related environmental sciences

Surface albedo partitions the amount of energy received by glacier surfaces from shortwave fluxes and modulates the energy available for melt processes. The ice-albedo feedback, influenced by the contamination of bare-ice surfaces with light-absorbing impurities, plays a major role in the melting of mountain glaciers in a warming climate. However, little is known about the spatial and temporal distribution and variability of bare-ice glacier surface albedo under changing conditions. In this study, we focus on two mountain glaciers located in the western Swiss Alps and perform a cross-comparison of different albedo products. We take advantage of high spectral and spatial resolution (284 bands, 2 m) imaging spectrometer data from the Airborne Prism Experiment (APEX) and investigate the applicability and potential of Sentinel-2 and Landsat 8 data to derive broadband albedo products. The performance of shortwave broadband albedo retrievals is tested and we assess the reliability of published narrow-to-broadband conversion algorithms. The resulting albedo products from the three sensors and different algorithms are further cross-compared. Moreover, the impact of the anisotropy correction is analysed depending on different surface types. While degradation of the spectral resolution impacted glacier-wide mean albedo by about 5%, reducing the spatial resolution resulted in changes of less than 1%. However, in any case, coarser spatial resolution was no longer able to represent small-scale variability of albedo on glacier surfaces. We discuss the implications when using Sentinel-2 and Landsat 8 to map dynamic glaciological processes and to monitor glacier surface albedo on larger spatial and more frequent temporal scales.