Abstract
This paper reviews and analyses the past 20 years of change and variability of European mountain permafrost in response to climate change based on time series of ground temperatures along a south–north transect of deep boreholes from Sierra Nevada in Spain (37°N) to Svalbard (78°N), established between 1998 and 2000 during the EU-funded PACE (Permafrost and Climate in Europe) project. In Sierra Nevada (at the Veleta Peak), no permafrost is encountered. All other boreholes are drilled in permafrost. Results show that permafrost warmed at all sites down to depths of 50 m or more. The warming at a 20 m depth varied between 1.5 °C on Svalbard and 0.4 °C in the Alps. Warming rates tend to be less pronounced in the warm permafrost boreholes, which is partly due to latent heat effects at more ice-rich sites with ground temperatures close to 0 °C. At most sites, the air temperature at 2 m height showed a smaller increase than the near-ground-surface temperature, leading to an increase of surface offsets (SOs). The active layer thickness (ALT) increased at all sites between c. 10% and 200% with respect to the start of the study period, with the largest changes observed in the European Alps. Multi-temporal electrical resistivity tomography (ERT) carried out at six sites showed a decrease in electrical resistivity, independently supporting our conclusion of ground ice degradation and higher unfrozen water content.
Highlights
Frozen ground is a globally widespread phenomenon with a coverage of more than 15% over the Northern Hemisphere land surface (Obu et al 2019)
All boreholes along the European latitudinal transect have warmed since the start of this century, down to depths of 50 m
Measurements at the sites in Scandinavia and the Alps reveal slightly reduced warming, which is mainly related to latent heat effects caused by relatively higher ice contents and by surface offsets (SOs) effects
Summary
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. B Etzelmüller1 , M Guglielmin2, C Hauck3, C Hilbich3, M Hoelzle3, K Isaksen4 , J Noetzli5, M Oliva6 and M Ramos7 Keywords: mountain permafrost, PACE, Europe, monitoring, climate change, recent warming
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have