Permafrost thermal regime and active layer dynamics across periglacial landforms in Svalbard's Nordenskiöld Land Permafrost Observatory, 2008–2023

On Spitsbergen, Svalbard, the Nordenskiöld Land Permafrost Observatory provides ground temperature time series from 2008 to the present in 16 boreholes located in a variety of periglacial landforms. This study presents trends in permafrost temperatures and active layer thickness, compares these trends to observed climatic changes, and differentiates the climate sensitivity of the studied periglacial landforms. Ground temperature variability in these landforms is driven by Svalbard's air temperature gradients due to elevation and from the warmer west coast to the colder interior, in addition to snow cover and landform dynamics. During the study period, increases in permafrost temperatures and active layer thickness, closely tied to rapid climate warming on Svalbard, were observed at nearly all sites. The observed rates of active layer thickness increase, ranging from 0.5 to 10.7 cm/year, are on the high end of observed values across the circum-Arctic. Decadal increase in temperature at 20 m depth reaches 0.9 °C; the Canadian High Arctic and the Beaufort–Chukchi region are the only Arctic areas with permafrost warming of comparable magnitude. The landforms that are entirely or predominately composed of bedrock or a blocky substrate are the most thermally sensitive to climate change.