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

Glaciers in the European Alps have experienced drastic area and volume loss since the end of the Little Ice Age (LIA) around the year 1850. How large these losses were is only poorly known, as published estimates of area loss are mostly based on simple upscaling and Alpine-wide reconstructions of LIA glacier surfaces are 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 digitising. This was based on geomorphologic interpretation of moraines and trimlines on very high-resolution images in combination with historic topographic maps and modern glacier outlines. Glacier area changes are determined for all glaciers with LIA extents at a regional scale. Glacier surface reconstruction with a geographic information system (GIS) was applied 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 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 −43.6 m until 2015 (−0.26 m a−1), which is 3 times less than observed over the 2000 to 2015 period (−0.82 m a−1). Many glaciers now have only remnants of their former coverage left, and at least 1938 glaciers melted away completely, which led to deglaciation of entire catchments. The new datasets should support a wide range of studies related to the determination of climate change impacts in the Alps, e.g. future glacier evolution, hydrology, land cover change, plant succession, and emerging hazards.