Past and future perturbation of the pan-Arctic terrestrial N feedback (PanArcN)

Thawing of Arctic permafrost soils enhances the release of greenhouse gases, which poses a serious threat for reaching climate goals set in the Paris Agreement. However, the comprehensive feedback arising from the region considering both the increased release of permafrost greenhouse gases, as well as vegetative greening trends currently ongoing in the Arctic, remains strongly uncertain. For instance, vast amounts of nitrogen (N) stored within permafrost soils may prove to strongly affect the high-latitude greenhouse gas exchange through its fertilization effects for the vegetation, or through enhancement of nitrous oxide emissions. To tackle this gap of knowledge, the proposed PanArcN project will use data from remote sensing and current field campaigns to determine the response of vegetation to deepening of the permafrost thaw depth and associated increasing N availability. The synthesis will be applied to enhance relevant inputs and parameters in the next-generation model QUINCY-ICON-Land, with the goal of projecting future changes in the pan-Arctic CO2 uptake and N2O emissions following a range of future scenarios. Finally, the effects that permafrost thaw and increased N availability have for the pan-Arctic greenhouse gas budget will be put into context against other regional factors that affect the region's greenhouse gas budget, such as enhanced warming and atmospheric CO2 fertilization. The work proposed here is highly relevant for improving quantifications of the uncertain permafrost feedback, and has important implications for global assessments of greenhouse gas budgets.