Observed snow depth trends in the European Alps: 1971 to 2019

Michael Matiu,Michael Winkler,Isabelle Gouttevin,Marc Zebisch,Ulrich Strasser,Gernot Resch,Andrea Sušnik,Daniele Cat Berro,Giorgia Marcolini,Viktor Weilguni,Giacomo Bertoldi,Silvia Terzago,Ludovica De Gregorio,Mauro Gaddo,Lorenzo Giovannini,Wolfgang Schöner,Andrea Debernardi,Alberto Trenti,Mauro Valt,Gabriele Chiogna,Bruno Majone,Simon C Scherrer,Samuel Morin,Walter Beozzo,Mattia Faletto,Luca Mercalli,Carlo Maria Carmagnola,Marcello Petitta,Christoph Marty,Alice Crespi,Stefano Urbani,Paola Cianfarra,Claudia Notarnicola,Sven Kotlarski,R Cremonini ,A Cicogna ,Jean Michel Soubeyroux

doi:10.5194/tc-15-1343-2021

Abstract

Abstract. The European Alps stretch over a range of climate zones which affect the spatial distribution of snow. Previous analyses of station observations of snow were confined to regional analyses. Here, we present an Alpine-wide analysis of snow depth from six Alpine countries – Austria, France, Germany, Italy, Slovenia, and Switzerland – including altogether more than 2000 stations of which more than 800 were used for the trend assessment. Using a principal component analysis and k-means clustering, we identified five main modes of variability and five regions which match the climatic forcing zones: north and high Alpine, north-east, north-west, south-east, and south and high Alpine. Linear trends of monthly mean snow depth between 1971 and 2019 showed decreases in snow depth for most stations from November to May. The average trend among all stations for seasonal (November to May) mean snow depth was −8.4 % per decade, for seasonal maximum snow depth −5.6 % per decade, and for seasonal snow cover duration −5.6 % per decade. Stronger and more significant trends were observed for periods and elevations where the transition from snow to snow-free occurs, which is consistent with an enhanced albedo feedback. Additionally, regional trends differed substantially at the same elevation, which challenges the notion of generalizing results from one region to another or to the whole Alps. This study presents an analysis of station snow depth series with the most comprehensive spatial coverage in the European Alps to date.

Highlights

In the European Alps, snow is pervasive throughout nature and human society
The first principal components (PCs) explained 54.3 % of the variance and distinguished between high- to middle- and low-elevation stations. It explained the variability in snow depth for stations above 1000 m and was probably partly linked to the permanence of snow cover, which is why some low-elevation sites presented similar loading to the high sites
Since the four regions were a compromise between all variables, they do not match perfectly to what we found for snow depth because the individual atmospheric variables exert different controls on surface snow cover

Summary

Introduction

In the European Alps, snow is pervasive throughout nature and human society. The mountain flora and fauna depend on the timing and abundance of snow cover (Esposito et al, 2016; Keller et al, 2005; Lencioni et al, 2011). Snow is tightly linked to human culture in the European Alps and has brought economic wealth to previously remote regions through tourism (Beniston, 2012a; Steiger and Stötter, 2013). Since snow cover depends on temperature and precipitation, ongoing climate change in the Alps and especially rising temperatures and changing precipitation patterns affect the abundance of snow (Beniston and Stoffel, 2014; Gobiet et al, 2014; Steger et al, 2013). Decreases are expected in the future, especially at low elevations with more uncertain trends in observations and future projections at higher elevation (Beniston et al, 2018; Hock et al, 2019; IPCC, 2019)

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