Titre et contributions: Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2 / Frank Paul [et al.]
Publication: Gottinga: Copernicus Publications, 2020
Testo elettronico (PDF) p.1805-1821 : ill.
eng (Langue du texte, du film, etc.)
- Autori: Frank Paul, Philipp Rastner, Roberto Sergio Azzoni, Guglielmina Diolaiuti, Davide Fugazza, Raymond Le Bris, Johanna Nemec, Antoine Rabatel, Mélanie Ramusovic, Gabriele Schwaizer, and
- 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%a1) 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 3000ma.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)