Recent warming of mountain permafrost in Svalbard and Scandinavia

Three deep boreholes (≥100 m) in mountain permafrost were recently drilled in Svalbard (Janssonhaugen) and in Scandinavia (Tarfalaryggen and Juvvasshøe) for long‐term permafrost monitoring. These holes form part of a latitudinal transect of boreholes in permafrost through Europe, established by the Permafrost and Climate in Europe (PACE) project. Six‐year thermal time series data collected from the three boreholes are presented. These data provide the first opportunity for temporal trends in permafrost temperatures in Svalbard and Scandinavia to be analyzed. Results show that the permafrost has warmed considerably at all three sites. Significant warming is detectable down to at least 60 m depth, and present decadal warming rates at the permafrost surface are on the order of 0.04°–0.07°C yr −1 , with greatest warming in Svalbard and in northern Scandinavia. The present regional trend shows accelerated warming during the last decade.