Modeling N2O emission from the pan-Arctic terrestrial ecosystems

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<p>Nitrous oxide (N<sub>2</sub>O) is a potent greenhouse gas with radiative forcing 265-298 times stronger than that of carbon dioxide (CO<sub>2</sub>). Increasing atmospheric N<sub>2</sub>O burden also contributes to stratospheric ozone depletion. Recent field studies show N<sub>2</sub>O emissions from the Arctic ecosystems have increased due to warming. To date, the emissions across space and time have not been adequately quantified.  Here we revised an extant process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM) to incorporate more detailed processes of soil biogeochemical nitrogen (N) cycle, permafrost thawing effects, and atmospheric N<sub>2</sub>O uptake in soils. The model is then used to analyze N<sub>2</sub>O emissions from pan-Arctic terrestrial ecosystems. We find that both regional N<sub>2</sub>O production and net emissions increased from 1969 to 2019, with production ranging from 1.2 - 1.3 Tg N yr <sup>-1 </sup>and net emissions from 1.1 - 1.2 Tg N yr<sup>-1 </sup>considering the permafrost thaw effects. Soil N<sub>2</sub>O uptake from the atmosphere was 0.1 Tg N yr <sup>-1</sup> with a small interannual variability. Atmospheric N deposition significantly increased N<sub>2</sub>O emission by 31.5 ± 3.1%.  Spatially, terrestrial ecosystems act as net sources or sinks ranging from -12 to 700 mg N m<sup>-2</sup> yr<sup>-1 </sup>depending on temperature, precipitation, soil characteristics, and vegetation types in the region.</p>
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