Abstract
Permafrost in the Arctic is thawing, exposing large carbon and nitrogen stocks for decomposition. Gaseous carbon release from Arctic soils due to permafrost thawing is known to be substantial, but growing evidence suggests that Arctic soils may also be relevant sources of nitrous oxide (N(2)O). Here we show that N(2)O emissions from subarctic peatlands increase as the permafrost thaws. In our study, the highest postthaw emissions occurred from bare peat surfaces, a typical landform in permafrost peatlands, where permafrost thaw caused a fivefold increase in emissions (0.56 ± 0.11 vs. 2.81 ± 0.6 mg N(2)O m(-2) d(-1)). These emission rates match those from tropical forest soils, the world's largest natural terrestrial N(2)O source. The presence of vegetation, known to limit N(2)O emissions in tundra, did decrease (by ∼90%) but did not prevent thaw-induced N(2)O release, whereas waterlogged conditions suppressed the emissions. We show that regions with high probability for N(2)O emissions cover one-fourth of the Arctic. Our results imply that the Arctic N(2)O budget will depend strongly on moisture changes, and that a gradual deepening of the active layer will create a strong noncarbon climate change feedback.