Permafrost, thermal conditions and vegetation patterns since the mid-20^th century: A remote sensing approach applied to Jotunheimen, Norway

Northern high-alpine regions are currently experiencing rapid warming, which often results in the degradation of sub-surface permafrost and upslope advancement vegetation. The present study combines remotely sensed MODIS Land Surface Temperatures (LSTs) Normalised Difference Vegetation Index (NDVI) with observed air temperatures to model thermal vegetational dynamics NE Jotunheimen (Norway) for period 1957–2019. An altitudinal transect on north-facing slope Galdhøpiggen was used ground truthing. Results indicate a substantial warming trend since late 1950s, accompanied by increased NDVI. spatial temporal patterns change were not uniform. Winter surface most rapidly, 2.4–2.8°C at mid- low altitudes (600–1500 m a.s.l.). highest increases NDVI (by ∼0.1) detected during growing season (April–September) over mid-range (1050–1500 a.s.l.), that is, above tree line Galdhøpiggen. We attribute this shrubification these altitudes. Our confirm near previously estimated lower limit (∼1450 a.s.l.) have continued increase past decade, likely facilitating further degradation. Finally, we demonstrate mapping mean LSTs below 0°C can be identify areas suitable continuous permafrost, June–September 7°C detect ( Betula pubescens) growth Jotunheimen.