Permafrost temperatures and active layer thickness in Svalbard during 2017/2018 (PermaSval)

This report follows up on the report published in the SESS Report 2018 (Christiansen et al. 2019). Since 2018, the Norwegian Environment Agency has released the Climate in Svalbard 2100 report summarizing observed trends in permafrost conditions over the period of field measurements and a forecast for the future, based on recent climate and permafrost modelling (Hanssen-Bauer et al. 2019). It is well established that the terrestrial cryosphere in Svalbard has changed since modern permafrost monitoring efforts began in the late 1990s. In central Svalbard in the Adventdalen area, ground temperatures have risen by as much as 0.15°C per year (10 m depth) and the thickness of the seasonally-unfrozen active layer increased by 0.6 cm per year since 2000 in sediments and 1.6 cm/year in bedrock (Hanssen-Bauer et al. 2019), while in Ny-Ålesund ground temperatures increased by 0.18°C/year and the thickness of active layer increased by 5 cm/year (Boike et al. 2018). Modern monitoring techniques mean that it is relatively easy to quantify permafrost change in terms of temperature. The visible effects of warming permafrost are, however, more ambiguous. A prolonged thaw season is anticipated to result in a thicker active layer, and increased rainfall intensity can result in more frequent landslides. The strength of frozen soil decreases when warming and permafrost change may expectedly result in infrastructure problems in cases where climate change was not considered during the initial design. The aims of this part of the State of Environmental Science in Svalbard reporting are to: (1) provide an overview of permafrost data collected during the 2017-2018 hydrological year (1 September 2017 – 31 August 2018), (2) contrast these results with the 2016-2017 hydrological year as presented in Christiansen et al. (2019), (3) summarise developments in permafrost monitoring in Svalbard, and (4) provide recommendations for future permafrost investigations. Understanding the spatial distribution of permafrost conditions is critical to predicting geomorphological change and understanding the variability in climate impacts. 2371