Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2

Abstract

Abstract. The ongoing glacier shrinkage in the Alps requires frequent updates of glacier outlines to provide an accurate database for monitoring, modelling purposes (e.g. determination of run-off, mass balance, or future glacier extent), and other applications. With the launch of the first Sentinel-2 (S2) satellite in 2015, it became possible to create a consistent, Alpine-wide glacier inventory with an unprecedented spatial resolution of 10 m. The first S2 images from August 2015 already provided excellent mapping conditions for most glacierized regions in the Alps and were used as a base for the compilation of a new Alpine-wide glacier inventory in a collaborative team effort. In all countries, glacier outlines from the latest national inventories have been used as a guide to compile an update consistent with the respective previous interpretation. The automated mapping of clean glacier ice was straightforward using the band ratio method, but the numerous debris-covered glaciers required intense manual editing. Cloud cover over many glaciers in Italy required also including S2 scenes from 2016. The outline uncertainty was determined with digitizing of 14 glaciers several times by all participants. Topographic information for all glaciers was obtained from the ALOS AW3D30 digital elevation model (DEM). Overall, we derived a total glacier area of 1806±60 km2 when considering 4395 glaciers >0.01 km2. This is 14 % (−1.2 % a−1) less than the 2100 km2 derived from Landsat in 2003 and indicates an unabated continuation of glacier shrinkage in the Alps since the mid-1980s. It is a lower-bound estimate, as due to the higher spatial resolution of S2 many small glaciers were additionally mapped or increased in size compared to 2003. Median elevations peak around 3000 m a.s.l., with a high variability that depends on location and aspect. The uncertainty assessment revealed locally strong differences in interpretation of debris-covered glaciers, resulting in limitations for change assessment when using glacier extents digitized by different analysts. The inventory is available at https://doi.org/10.1594/PANGAEA.909133 (Paul et al., 2019).

Comment on tc-2021-31

“…The latter is also confirmed by the comparison of the total ice volume change 2000-2020 in Switzerland (comprising almost 60% of the Alpine glacier volume at present): estimated as 23.6 km 3 based on observational series (Grab et al, submitted), it is very close to our modelled loss of 24.9 km 3 . Similarly, the modelled rate of glacier area loss (1.4 % a −1 for the period 2003-2016) is in very good agreement with the rate of 1.3 % a −1 derived by Paul et al (2020) using Landsat images.…”

200 years of equilibrium-line altitude variability across the European Alps (1901−2100)

“…The 4395 glaciers currently still present in the Alps with a total area of 1806 ± 60 km 2 (Paul et al 2020) are projected to lose a substantial part of their volume in the coming Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s0038 2-020-05525 -7) contains supplementary material, which is available to authorized users. century and many of them are expected to disappear by 2100 regardless of which emission scenario is used (Haeberli and Hoelzle 1995;Zemp et al 2006Zemp et al , 2007.…”

Unprecedented loss of surface and cave ice in SE Europe related to record summer rains in 2019

“…CC BY 4.0 License. thunderstorms, and surface glaciers close to the 0 ° isotherm, thus resulting in the loss of ice faster than predicted by the most recent estimates (IPCC, 2019;Paul et al, 2020).…”