Impacts of Permafrost Degradation on N2O Emissions From Natural Terrestrial Ecosystems in Northern High Latitudes: A Process-Based Biogeochemistry Model Analysis

Abstract

Nitrous oxide (N2O) is a potent greenhouse gas with its radiative forcing 265–298 times stronger than that of carbon dioxide (CO2). Recent field studies show N2O emissions from northern high latitude (north of 45°N) ecosystems have increased due to warming. However, spatiotemporal quantification of N2O emissions remains inadequate in this region. Here we revise the Terrestrial Ecosystem Model to incorporate more detailed processes of soil nitrogen (N) biogeochemical cycling, permafrost thawing effects, and atmospheric N deposition. Terrestrial Ecosystem Model is then used to analyze N2O emissions from natural terrestrial ecosystems in the region. Our study reveals that regional N2O production and net emissions increased from 1969 to 2019. Production rose from 1.12 (0.82–1.46) to 1.18 (0.84–1.51) Tg N yr−1, while net emissions increased from 0.98 (0.7–1.34) to 1.05 (0.72–1.39) Tg N yr−1, considering permafrost thawing. Emissions from permafrost regions grew from 0.37 (0.2–0.57) to 0.41 (0.21–0.6) Tg N yr−1. Soil N2O uptake from the atmosphere remained relatively stable at 0.12 (0.1–0.15) Tg N yr −1. Atmospheric N deposition significantly increased N2O emission by 37.2 ± 2.9%. Spatially, natural terrestrial ecosystems act as net sources or sinks of −12 to 900 mg N m−2 yr−1 depending on changing temperature, precipitation, soil characteristics, and vegetation types. Our findings underscore the critical need for more observational studies to reduce the uncertainty in N2O budget.