Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method

The microbial by-product nitrous oxide (N₂O), a potent greenhouse gas and ozone depleting substance, has conventionally been assumed to have minimal emissions in permafrost regions. This assumption has been questioned by recent in situ studies which have demonstrated that some geologic features in permafrost may, in fact, have elevated emissions comparable to those of tropical soils. However, these recent studies, along with every known in situ study focused on permafrost N₂O fluxes, have used chambers to examine small areas (<50 m²). In late August 2013, we used the airborne eddy-covariance technique to make in situ N₂O flux measurements over the North Slope of Alaska from a low-flying aircraft spanning a much larger area: around 310 km². We observed large variability of N₂O fluxes with many areas exhibiting negligible emissions. Still, the daily mean averaged over our flight campaign was 3.8 (2.2–4.7) mg N₂O m⁻² d⁻¹with the 90 % confidence interval shown in parentheses. If these measurements are representative of the whole month, then the permafrost areas we observed emitted a total of around 0.04–0.09 g m⁻² for August, which is comparable to what is typically assumed to be the upper limit of yearly emissions for these regions.