Towards long-term SWE and snow melt trends for Europe

Abstract:

There is strong evidence that rising temperatures mostly lead to less snow accumulation and to an earlier melt onset. However, changes in the frequency and intensity of snowmelt events remain unclear. While higher temperatures should intuitively lead to faster snowmelt, some studies find that melt rates are slower because the melt onset occurs earlier in the year when less energy is available for melt. Modelling of these snow dynamics is challenged by a lack of observations on water content of the snowpack, the highly sought after SWE. However, high quality observations of snow depth can be more available in both space and time, even at higher altitudes. An increasing number of models try to estimate SWE from snow depth by estimating snow density based on type of climate, elevation, and day of the year. Here we convert a long-term pan-European snow depth dataset to SWE using a variety of these models. We analyse both model performance and multi-model agreement. Long- and short-term trends of snowmelt rates, melt onset, and frequency and intensity of melt events are shown for over 300 seasonal snow locations across Europe. Trends across a variety of timescales are generally weak and spatially inhomogeneous, suggesting local conditions dominate over regional climate trends, with a few exceptions especially in the Alpine region showing a trend towards slower snowmelt.