Bearing the brunt of warming: Interactions between carbon and hydrology in northern Sweden

Abstract: Climate modelling studies indicate that subarctic ecosystems are predicted to show some of the earliest responses to climate change. The predicted temperature and precipitation changes have implications for the carbon biogeochemical cycle with ancillary effects in permafrost soils, vegetation, and stream networks. Browning, a result of changes in dissolved organic carbon (DOC) export to river systems, has been marked as an early indicator of climate-induced changes in northern freshwaters. The release of DOC in to rivers and atmosphere has the potential to further increase the emissions of greenhouse gasses. The reintroduction of old carbon is not limited to atmospheric interactions as the lateral flux of carbon at the terrestrial-aquatic interface is further affected by warming. Parts of the subarctic region are host to permafrost soils, which serve as a store of frozen soil organic carbon. Climatic changes threaten to turn these regions from carbon sinks to carbon sources. Active layer deepening, a result of precipitation and temperature changes in permafrost zones, is a source of increasing greenhouse gas (CO2 and CH4) emissions. Changes in of permafrost areas spurs changes in catchment land cover and ecosystem function.This study was conducted in a subarctic catchment with mixed vegetation cover and a permafrost thaw gradient to understand the spatio-temporal changes in the biogeochemical cycle. The Normalized Vegetation Difference Index (NDVI), together with easily available topographical indices, was used to model the DOC release into streams using GIS analysis and linear regression methods. The results of this research show that DOC is concentrated in the low-lying areas of Stordalen catchment. The distribution of DOC was largely controlled by topographic factors, in particular slope and the presence of mires. This study points to a largely unexplored potential of using geospatial analysis methods to capture and represent responses to climate change. Applying geospatial techniques provides a first step spatio-temporal approach to present phase shifts in the broader scale of catchment carbon cycling.