Abstract
This study focuses on an assessment of the future snow
depth for two larger Alpine catchments. Automatic weather station data from
two diverse regions in the Swiss Alps have been used as input for the
Alpine3D surface process model to compute the snow cover at a 200 m
horizontal resolution for the reference period (1999–2012). Future
temperature and precipitation changes have been computed from 20 downscaled
GCM-RCM chains for three different emission scenarios, including one
intervention scenario (2 °C target) and for three future time
periods (2020–2049, 2045–2074, 2070–2099). By applying simple daily change
values to measured time series of temperature and precipitation, small-scale
climate scenarios have been calculated for the median estimate and extreme
changes. The projections reveal a decrease in snow depth for all elevations,
time periods and emission scenarios. The non-intervention scenarios
demonstrate a decrease of about 50 % even for elevations above 3000 m.
The most affected elevation zone for climate change is located below 1200 m,
where the simulations show almost no snow towards the end of the century.
Depending on the emission scenario and elevation zone the winter season
starts half a month to 1 month later and ends 1 to 3 months earlier
in this last scenario period. The resulting snow cover changes may be
roughly equivalent to an elevation shift of 500–800 or 700–1000 m for the
two non-intervention emission scenarios. At the end of the century the
number of snow days may be more than halved at an elevation of around 1500 m
and only 0–2 snow days are predicted in the lowlands. The results for the
intervention scenario reveal no differences for the first scenario period
but clearly demonstrate a stabilization thereafter, comprising much lower
snow cover reductions towards the end of the century (ca. 30 % instead of
70 %).