Assessment of future snow pack in two Alpine regions

The snow cover in the Alps is heavily affected by climate change. In this study we present an assessment of the future snow water equivalent and snow depth for the Swiss Canton of Graubünden and the Aare catchment in the central Swiss Alps. The data of 48 automatic weather stations in the Aare catchment, respectively 34 automatic weather stations in Graubünden, have been used as the input for Alpine3D, a spatially distributed model for the highresolution simulation of alpine surface processes. These catchments have been modeled at 200 m horizontal resolution for a 13 years reference period (1999-2012). Three different emission scenarios for temperature and precipitation (A2, A1B and RCP3PD) and for three different time periods (2020-49, 2045-74, 2070-99) have been taken from the Swiss Climate Change scenarios CH2011 Plus. By applying simple daily shifts of temperature and precipitation to the measured time series, input for the smallscale climate scenarios has been generated. The model results show a decrease smaller than 20 % in the snow depth for the first time period 2020-49 for all three emission scenarios. For the time 2070-99 however, the relative decrease in snow depth is as high as 70 % for the A2 scenario. The most sensible elevation zone for climate change is located around 800–1200 m, where the simulations show almost no snow for 2070-99. The winter season starts, depending on the emission scenario and the elevation zone, 2-4 weeks later and ends 5-8 weeks earlier. Towards the end of the century the snow cover changes will roughly be equivalent to an elevation shift of 500-700 m or 600-900 m for A1B or A2, respectively. The number of snow days will be halved at an elevation of around 1500 m and is predicted to 0-2 snow days in the Swiss Plateau and the low Rhine valley in Graubünden. The A2 scenario projects a catchment-wide snow water equivalent reduction of up to two thirds towards the end of the century. These changes in snow duration and snow amount will affect changes in the melt water runoff, which has important consequences for winter tourism and hydropower generation.