Climate change - Declining snowpack

University of Neuchâtel/ WSL Institute for Snow and Avalanche Research SLF / Swiss Federal Institute for Forest, Snow and Landscape Research WSL

A recent study by the University of Neuchâtel, the WSL Institute for Snow and Avalanche Research SLF and the Swiss Federal Research Institute WSL shows that the seasonal duration of snowpack in the Swiss Alps has decreased since 1970, even at high altitudes. The primary cause lies in earlier springtime snowmelt.

Climate warming has noticeable wintertime effects, and exerts a proportionate influence on the seasonal snowpack, as illustrated by a study recently published by the University of Neuchâtel and the WSL Institute for Snow and Avalanche Research SLF. A research team headed by Martine Rebetez provides evidence for the first time that the snow season at altitudes between approximately 1100 and 2500 m has shortened in recent decades. Until now such conclusions have been applicable only to individual stations and other periods.

For the new study, the researchers selected 11 MeteoSwiss weather stations in highly diverse Alpine regions of Switzerland and analysed the period from 1970 to 2015. Some of the data used in the project were collected by the SLF, including at the high-altitude Weissfluhjoch station (2540 m) above Davos. A considerable reduction in the snow cover duration was observed at all stations, regardless of altitude and geographical location. The primary cause was found to be earlier snow disappearance in the spring; however, the delay of snow onset in autumn is also relevant. At all stations the average date for the onset of the snow season is now 12 days later, and the season ends around 25 days earlier than in 1970. Snow cover duration is thus contracting twice as fast in spring as it is in autumn. The researchers also discovered that annual maximum snow depth has decreased by 25 percent on average and is reached 28 days earlier than 45 years ago.

Although exceptionally large quantities of snow fell during the winters of the early 1970s, which magnifies the contrast to more recent data, the change is nonetheless dramatic. Martine Rebetez says, "These recent results show that the snow cover duration has been reduced not only at low altitudes, where the change is immediately apparent to everyone, but in all altitude zones which we investigated, particularly in the spring." The study findings do not indicate the extent to which the trend is likely to be amplified in future years, but the effects can be expected to have an impact on both winter sport activities and the water resources available to communities and ecosystems in summertime.

Geoffrey Klein, University of Neuchâtel / WSL
geoffrey.klein(at)unine.ch