The Potential of Earth Observation to Assess the Impact of Climate Change on the Alpine Snow Line Elevation

Abstract

Snow plays a crucial environmental, societal and economical role in mountainous regions. It has an important impact on the local climate due to its albedo, strongly influences natural habitats, ensures the availability of freshwater and, last but not least, is the basis for the tourism-based economies of entire regions. At the same time, mountainous regions and especially snow cover are subject to dramatic changes in the context of climate change. These can be observed continuously at variable spatial scales using remote sensing. Long-term satellite missions such as the multispectral Landsat sensor family have been recording dynamics on the Earth's surface at high-resolution for almost 40 years. From this openly accessible data archive we have derived monthly time series of Snow Line Elevation (SLE) dynamics on a catchment basis for the entire Alps from 1985 until today. This multi-decadal SLE dataset is utilized in a variety of ways: We analyzed long-term trends of SLE which was found to be retreating to higher elevations at rates of several meters per year in a majority of the Alpine catchments. In the context of the drought in Northern Italy we compared the SLE dynamics of early 2022 to the long-term observations and found the SLE to be located up to almost 1000m higher than usual. Based on these findings we discussed the SLE as a complementary parameter in drought early warning systems. Ultimately, we aim at the prediction and projection of future spatio-temporal SLE dynamics in the context of climate change. To do this, we are currently identifying and assessing the environmental drivers of Alpine SLE dynamics in an extensive time-series correlation analysis. First results show that the strongest linear links exist between SLE and temperature as well as snow related variables such as snow cover fraction and snow depth, and that the correlation strength can vary considerably between different regions. These efforts will contribute to estimations about Alpine snow cover change in the future and its impacts on natural habitats, the occurrence of hydrological droughts, or snow reliability for winter tourism under a changing climate.