The volume of Swiss glaciers continues to decline in summer 2020. Although it is not an extreme year, the decline remains significant and is drastically changing the image of the Alps. Since 1960, Swiss glaciers have lost so much water that Lake Constance could be filled with it, as reported by the Cryospheric Commission CC of the Swiss Academy of Sciences. At low altitudes, winter of 2019/20 was characterized by less snow than ever before.
In the last decade, glacier melt has been stronger than ever since observations began. In 2020, the loss will continue but thanks to a slightly milder summer it will not be equally dramatic throughout Switzerland. At the beginning of May, there was snow on the glaciers, which was about the average of the last 10 years. However, snow on glacier tongues became depleted early, and the melt reached very high values. In September 2020, the lowest depth of the snow was measured on Great Aletsch Glacier close to Jungfraujoch since measurements began 100 years ago. However, the situation of most glaciers was not as serious as the period from 2017 to 2019. Nevertheless, almost 2 percent of the total glacier volume has been lost throughout Switzerland over the last 12 months – the negative trend is continuing.
The retreat of the glacier changes the landscape
Measurements of winter snowfall and melt on more than 20 glaciers in all parts of the country show significant differences in losses. While low-lying, flat glaciers (e.g. Glacier de Tsanfleuron, VS) recorded an average reduction of 2 metres in ice thickness, glaciers at high altitudes in the southern Valais as well as in Ticino and Engadine (e.g. Findel Glacier, Ghiacciaio del Basòdino) lost only about 0.5 metres in thickness. There this is due to a lot of snow in early winter and snowfall in summer.
Since 1960, Swiss glaciers have lost so much water that Lake Constance could be filled with it. This has significantly changed the landscape of the Alps - glacier forelands are growing, and new mountain lakes are being created. Individual small glaciers had to be removed from the monitoring network due to their disintegration (e.g. Vadret dal Corvatsch, GR). The retreat of the glacier also creates dangers as impressively illustrated by the ice break-off at the Turtmann Glacier, VS and the emptying of the glacial lake on Plaine Morte, BE.
Winter with extremely low snowfall at low altitudes
With heavy snowfalls at the beginning of November 2019, snowfall in the mountains occurred about two weeks earlier than normal. On the southern slopes of the Alps, new November highs of new snow totals were recorded in some cases. The temperature in the winter months from December to February was record high with over +3°C. Also the spring was clearly hot and characterised by a lot of sunshine. This means that below 1000 metres, precipitation fell for the most part as rain during the entire winter half-year – the little snow that fell remained at most for a few hours or days. In this altitude range, the winter with the least amount of snowfall occurred since the beginning of the measurements – worse than the winters of 1989/90 and 2006/07. For the first time, no new snow could be recorded at the low-lying stations in Central Switzerland, Altdorf, Stans and Lucerne (beginning of measurements: 1883). Between 1000-1700 metres above sea level, the depths of snow were between 10-90 percent lower than the average of 1981-2010 almost everywhere. Above 1700 metres, the depths of snow were average, while in the northern Ticino and southern Valais they were sometimes above average.
Hot summer with less snowfall in the Alps
In June, snowfall delayed the already advanced ablation of snow cover at high altitudes. With the exception of the stations in southern Valais, the disappearance of the snow cover occurred 1-4 weeks earlier than normal. The period from July to September was once again characterised by above-average temperatures. In contrast to the last two years, however, there was fresh snow twice down to 2000 metres as early as August. At the end of September, the snow line on the northern side of the Alps fell in some cases to below 1000 metres. Above this, 20-30 cm of fresh snow was registered, which is unusual for this time of the year.
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.