Extrapolating glacier mass balance to the mountain-range scale: the European Alps 1900–2100

Abstract. This study addresses the extrapolation of in-situ glacier mass balance measurements to the mountain-range scale and aims at deriving time series of area-averaged mass balance and ice volume change for all glaciers in the European Alps for the period 1900–2100. Long-term mass balance series for 50 Swiss glaciers based on a combination of field data and modelling, and WGMS data for glaciers in Austria, France and Italy are used. A complete glacier inventory is available for the year 2003. Mass balance extrapolation is performed based on (1) arithmetic averaging, (2) glacier hypsometry, and (3) multiple regression. Given a sufficient number of data series, multiple regression with variables describing glacier geometry performs best in reproducing observed spatial mass balance variability. Future mass changes are calculated by driving a combined model for mass balance and glacier geometry with GCM ensembles based on four emission scenarios. Mean glacier mass balance in the European Alps is −0.31 ± 0.04 m w.e. a⁻¹ in 1900–2011, and −1 m w.e. a⁻¹ over the last decade. Total ice volume change since 1900 is −96 ± 13 km³; annual values vary between −5.9 km³ (1947) and +3.9 km³ (1977). Mean mass balances are expected to be around −1.3 m w.e. a⁻¹ by 2050. Model results indicate a glacier area reduction of 4–18% relative to 2003 for the end of the 21st century.