Evaluation of High Arctic terrestrial habitats as potential hotspots of nitrous oxide emissions (Hornsund region, South Spitsbergen)

Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are the main greenhouse gases (GHGs) contributing to the ongoing climate crisis. Among those N2O has the highest global warming potential and is mainly of microbiological origin. Tropical rainforests are considered the primary natural source, although in recent years fluxes of N2O from polar ecosystems have been reported at comparable levels. In this study we aimed to identify High Arctic terrestrial habitats with the highest potential to become sources of N2O emissions. A microbiological and geochemical analysis was performed on soil procured from the biologically and geomorphologically diverse South Spitsbergen region in search of biotic and abiotic determinants of a N2O emission hotspot. Terrestrial sites within this High Arctic area vastly differed in their potential to emit substantial N2O amounts. External organic matter inputs were pivotal in maintaining a pool of inorganic nitrogen compounds for microbially-mediated N2O-generating processes such as denitrification. The examined planktivorous seabird colony presented a unique, potential N2O emission hotspot as it featured persistent acidification of the surrounding soil, a steady ammonia release and nitrate presence even after breeding season closure. Soils of the majority of analyzed sites did not display detectable nitrate and/or ammonia levels, with some areas having the characteristics of a N2O-sink rather than an emitter, especially postglacial moraine deposits. The presented data encourage further, more targeted investigations of High Arctic N2O emission hot- and coldspots to progressively improve N2O emission estimates for permafrost affected regions worldwide.