Reconstructed glacier area and volume changes in the European Alps since the Little Ice Age

Glaciers in the European Alps have experienced strong area and volume loss since the end of the Little Ice Age (LIA) around the year 1850. How large these losses were was so far only poorly known, as published estimates of area loss were mostly based on simple up-scaling and alpine-wide reconstructions of LIA glacier surfaces were lacking. For this study, we compiled all digitally available LIA glacier extents for the Alps and added missing outlines for glaciers >0.1 km2 by manual digitizing. This was based on geomorphologic interpretation of moraines and trimlines on very high-resolution satellite images available from web-map services in combination with historic topographic maps and modern glacier outlines.From this dataset we determined glacier area changes for all glaciers with LIA extents at a regional scale and reconstructed glacier surfaces with a Geographic Information System (GIS) to calculate (a) glacier volume changes for the entire region from the LIA until around 2015 and (b) total LIA glacier volume in combination with a reconstructed glacier bed. The glacier area shrunk from 4244 km2 at the LIA maximum to 1806 km2 in 2015 (-57%) and total volume was reduced from about 280±43 km3 around 1850 to 100±17 km3 (-64%) in 2015, roughly in line with previous estimates. On average, glacier surfaces lowered by 44 m from the LIA until 2015 (-0.26 m a-1), which is three-times less than observed over the 2000 to 2015 period (-0.82 m a-1) according to Hugonnet et al. (2021). Many glaciers have now only remnants of their former coverage left and at least 1938 glaciers melted away completely, which led to the deglaciation of entire mountain catchments.The new datasets are made freely available to support a wide range of studies related to the determination of climate change impacts in the Alps. We will present the different input datasets and their uncertainties, the method applied to reconstruct glacier surfaces and the spatial variability of glacier area and volume changes in the Alps since the LIA.