Near-decadal changes in active layer depth in Stordalen mire, Sweden

Active layer deepening, a result of precipitation and temperature changes, in the discontinuous permafrost zone (at northern latitudes) is a source of increasing CO₂ and CH₄ emissions. The reintroduction of old carbon is not limited to atmospheric interactions as the lateral flux of carbon from terrestrial systems to river networks is important. Specifically, northern peatlands (which have a large C store) are shifting their function from net carbon sinks to carbon sources. In this study we present an eight year response of peatland permafrost thaw at 30 sites in Stordalen mire, focusing on active layer (ALD) and water table depth (WTD) changes using geospatial analysis and remote sensing techniques. We further use changes in ALD and WTD in the mire to show, through hydrological modelling, the expansion of the stream network in the catchment. Preliminary annual comparison of seasonal inverse distance weighted surfaces shows that there is a progressive increase in ALD starting at sites in the south east of the catchment. This corresponds to a median of 52 cm for sites on the NW-SE axis and 64 cm for sites on the NNW-WSW axis. Results of hydrological modelling on the permafrost table (PFT) indicate that drainage network entrenchment is most dominant in the NE-SW direction with an emergent channel in the E-W direction (mostly fen sites). We use our findings together with hydrological export and efflux data to report the influence that ALD and WTD changes have in Stordalen. Permafrost degradation is ongoing across sites at northern latitudes; applying geospatial techniques provides a first step spatio-temporal approach to present phase shifts in the broader scale of catchment carbon cycling.