25 years permafrost monitoring in the Swiss Alps

Permafrost is classified as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS) because of its sensitivity to changes in climatic conditions. The Swiss Permafrost Monitoring Network PERMOS documents the state and changes of permafrost conditions in the Swiss Alps since 2000 based on long-term field measurements. To account for the heterogeneous distribution and characteristics of mountain permafrost, PERMOS developed and implemented a comprehensive monitoring strategy, which relies on three complementary observation elements: (1) direct observation of ground temperatures, (2) permafrost electrical resistivity to determine changes in ground ice content, and (3) rock glacier velocities, which are considered a proxy to assess the permafrost thermal regime.

In this contribution, we discuss permafrost conditions in the Swiss Alps during the hydrological year 2024 with respect to the observations of the past 25 years. Striking changes in permafrost conditions were recorded for all three observation elements. Most recently, the hydrological year 2024 was characterized by the warmest winter on record since 1864 and by an early onset of the snow cover in autumn 2023 following a hot summer. These atmospheric conditions led to the warmest permafrost conditions since the start of the measurements revealed by all observation elements.