Abstract
Continuous monitoring of glacier changes supports our understanding of climate related glacier behavior. Remote sensing data offer the unique opportunity to observe individual glaciers as well as entire mountain ranges. In this study, we used synthetic aperture radar (SAR) data to monitor the recession of wet snow area extent per season for three different glacier areas of the Rofental, Austria. For four glaciological years (GYs, 2014/2015–2017/2018), Sentinel-1 (S1) SAR data were acquired and processed. For all four GYs, the seasonal snow retreated above the elevation range of perennial firn. The described processing routine is capable of discriminating wet snow from firn areas for all GYs with sufficient accuracy. For a short in situ transect of the snow—firn boundary, SAR derived wet snow extent agreed within an accuracy of three to four pixels or 30–40 m. For entire glaciers, we used optical remote sensing imagery and field data to assess reliability of derived wet snow covered area extent. Differences in determination of snow covered area between optical data and SAR analysis did not exceed 10% on average. Offsets of SAR data to results of annual field assessments are below 10% as well. The introduced workflow for S1 data will contribute to monitoring accumulation area extent for remote and hazardous glacier areas and thus improve the data basis for such locations.
Highlights
Changes in glacier mass balance are commonly used as indicators of global climate change [1]
These studies failed at monitoring the temporal evolution of the accumulation area ratio (AAR) once the transient snowline retreated above perennial firn areas
Deviations to the extent of snow covered areas derived from visual and shortwave infrared channels are less than 10% (8.5%) in area for C-band data
Summary
Changes in glacier mass balance are commonly used as indicators of global climate change [1]. Previous studies (e.g., [12,13]) mentioned that the discrimination of snow and firn for C-band SAR data is impossible for utilizing co-polarized channels In consequence, these studies failed at monitoring the temporal evolution of the accumulation area ratio (AAR) once the transient snowline retreated above perennial firn areas. These studies failed at monitoring the temporal evolution of the accumulation area ratio (AAR) once the transient snowline retreated above perennial firn areas Such retreat occurs primarily in years of strong negative mass balances. Once the relationships have been established and evaluated, reliable AAR estimates from SAR data enable predictions of B solely from remote sensing Such data help to assess and quantify runoff from glacierized catchments as snow, firn and ice have different surface albedos and, melt rates are varying [17]. For Vernagtferner and Hintereisferner, the identified relation between AAR and B were compared with the existing field observations
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