Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost

International audienceAs high latitudes warm, vast stocks of carbon and nitrogen stored in permafrost will become available for transport to aquatic ecosystems. While there is a growing understanding of the potential effects of permafrost collapse (thermokarst) on aquatic biogeochemical cycles, neither the spatial extent nor temporal duration of these effects is known. To test hypotheses concerning patterns and persistence of elemental export from upland thermokarst, we sampled hydrologic outflow from 83 thermokarst features in various stages of development across the North Slope of Alaska. We hypothesizedthat an initial pulse of carbon and nutrients would be followed by a period of elemental retention during feature recovery, and that the duration of these stages would depend on feature morphology. Thermokarst caused substantial increases in dissolved organic carbon a water chemistry differed by feature type and secondarily by landscape age. Most solutes returned to undisturbed concentrations after feature stabilization, but elevated dissolved carbon, inorganic nitrogen, and sulfate concentrations persisted through stabilization for some feature types, suggesting that aquatic disturbance by thermokarst for these solutes is longlived. Dissolved methane decreased by 90% for most feature types, potentially due to high concentrations of sulfateand inorganic nitrogen. Spatial patterns of carbon and nutrient export from thermokarst suggest that upland thermokarstmay be a dominant linkage transferring carbon and nutrients from terrestrial to aquatic ecosystems as the Arctic warms