The volume of Swiss glaciers decreased by almost 1 percent in 2021, in spite of plentiful snow in winter and a pretty cool summer. Despite considerable precipitation in summer, there was hardly any fresh snow in the Alps. All this shows the impact of climate change, reports the Cryospheric Commission (CC) of the Swiss Academy of Sciences.
The retreat of Swiss glaciers over the last three decades has been immense – one extreme year followed by the next. In terms of weather, the conditions were right in 2021 to give the glaciers a breather. Unfortunately, in times of climate change, even a "good" year is not good enough for the glaciers: The loss of ice continued, albeit at a slower pace, despite abundant snow in the winter and a comparatively cool and mixed summer weather. At the end of April, most glaciers had only slightly above-average snowfall. However, May brought a lot of additional snow in the high mountains. On the Claridenfirn (GL, 2890 m), a snow depth of almost 7 metres was then measured – the highest value since observations began in 1914. Thus, the glaciers were relatively well protected by winter snow until the rainy month of July. Nevertheless, the melt had been considerable by the end of September, and throughout Switzerland some 400 million tonnes of ice had been lost over the last 12 months, almost 1% of the remaining glacier volume.
Lowest ice loss since 2013
Measurements by the Swiss glacier monitoring network GLAMOS document ice loss on all 22 glaciers measured. Although the losses were smaller than in recent years, no gains were recorded for any of the glaciers. Particularly in the northern Valais (the Rhone and Great Aletsch glaciers), the decrease in mean ice thickness is moderate at just under 0.2 metres. In southern Valais, Ticino and north-eastern Switzerland (e.g. the Findel and Silvretta glaciers), on the contrary, losses are hardly lower than the average of the last 10 years. While considerable snow reserves, i.e. "food" for the glacier, were measured on large glaciers above around 3,200 m in autumn, lower-lying glaciers are in part completely depleted again without any sign of reversal. Even though 2021 shows the lowest ice loss since 2013, there is no relief in sight for glacier retreat.
Snowy winter down to the lowlands
Above 2,300 m, the snow came and stayed as early as the end of September 2020 in many places, below that altitude at the beginning of December at the latest. The repeated snowfalls between December and February down to the lowlands were then not so much due to the amount of precipitation, but thanks to the lucky combination of precipitation and sufficiently cold temperatures. The temperature from November to April was at the average of the last 30 years. The total precipitation in the winter months was above average on both sides of the Alps, but lower than normal in March and April. Over the winter half-year as a whole, snow depths were above average in eastern Switzerland and Graubünden, and average in the rest of Switzerland, with the exception of the low elevations in western Switzerland. Due to a cool April and May, the melting of the snow at the measuring stations at high altitudes took place about 1-2 weeks later than normal.
Wet summer but hardly any fresh snow in the Alps
According to MeteoSwiss, the summer months of 2021 north of the Alps are among the wettest on record in over 100 years. Temperatures were in the range of the mean value of the last three decades, which, nevertheless, means elevated temperature of 1.8°C compared to the standard period 1961-1990. The impact of climate change is clearly evident in the total fresh snow volumes in summer, which are surprisingly low despite a lot of precipitation: The Weissfluhjoch (GR, 2540 m), for example, recorded 155 cm of fresh snow during the very wet summer of 1987; in 2021 it was only 20 cm. Accordingly, no total fresh snow volumes of over 50 cm were recorded anywhere, even at the highest measuring stations. The very warm and sunny September 2021 brought only two small fresh snowfalls in the mountains.
The Swiss Glacier Monitoring Network (GLAMOS) is financed by the Federal Office for the Environment (FOEN), the Federal Office of Meteorology and Climatology MeteoSwiss within the framework of GCOS Switzerland, the Swiss Academy of Sciences and swisstopo.
Dr. Matthias Huss
University of Fribourg
Chemin du Musée 4