No abstract

This study investigates the impacts of active layer detachments (ALDs) on nitrogen in seasonal runoff from High Arctic hillslope catchments. We examined dissolved nitrogen in runoff from an undisturbed catchment (Goose (GS)) and one that was disturbed (Ptarmigan (PT)) by ALDs, prior to disturbance (2007) and 5 years after disturbance (2012). The seasonal dynamics of nitrogen species concentrations and fluxes were similar in both catchments in 2007, but the mean seasonal nitrate concentration and mass flux from the disturbed catchment were on the order of 30 times higher relative to the undisturbed catchment in 2012. Stormflow yielded 45% and 60% of the 2012 total dissolved nitrogen flux in GS and PT, respectively, although rainfall runoff provided less than 25% of seasonal discharge. Results support that through the combined effects of increased disturbance and rainfall, climate change stands to significantly enhance the export of nitrate from High Arctic watersheds. This study highlights that the increase in the delivery of nitrate from disturbance is especially pronounced late in the season when downstream productivity and the biological demand for this often limiting nutrient are high. Our results also demonstrate that the impact of ALDs on nitrate export can persist more than 5 years following disturbance.Key words: dissolved nitrogen, active layer detachment, precipitation, nitrate, High Arctic.Résumé : Cette étude analyse les effets des détachements de la couche active (DCA) sur la teneur en azote dans l'écoulement saisonnier provenant des bassins versants des sommets du Haut-Arctique. Nous avons examiné l'azote dissous dans l'écoulement d'un bassin versant calme (Goose) (GS) et d'un bassin qui a été perturbé (Ptarmigan) (PT) par les DCA, et ce, avant la perturbation (2007) For personal use only.substance nutritive limitante sont élevées. Nos résultats démontrent aussi que l'impact des DCA sur l'exportation de nitrate peut persister plus de 5 ans après la perturbation.Mots-clés : azote dissous, détachement de la couche active, précipitation, nitrate, Haut-Arctique.