Abstract
Arctic wetlands and surrounding ecosystems are both a significant source of methane (CH4) and a sink of carbon dioxide (CO2) during summer months. However, precise quantification of this regional CH4 source and CO2 sink remains poorly characterized. A research flight using the UK Facility for Airborne Atmospheric Measurement was conducted in July 2019 over an area (approx. 78 000 km2) of mixed peatland and forest in northern Sweden and Finland. Area-averaged fluxes of CH4 and carbon dioxide were calculated using an aircraft mass balance approach. Net CH4 fluxes normalized to wetland area ranged between 5.93 ± 1.87 mg m−2 h−1 and 4.44 ± 0.64 mg m−2 h−1 (largest to smallest) over the region with a meridional gradient across three discrete areas enclosed by the flight survey. From largest to smallest, net CO2 sinks ranged between −513 ± 74 mg m−2 h−1 and −284 ± 89 mg m−2 h−1 and result from net uptake of CO2 by vegetation and soils in the biosphere. A clear gradient of decreasing bulk and area-averaged CH4 flux was identified from north to south across the study region, correlated with decreasing peat bog land area from north to south identified from CORINE land cover classifications. While N2O mole fraction was measured, no discernible gradient was measured over the flight track, but a minimum flux threshold using this mass balance method was calculated. Bulk (total area) CH4 fluxes determined via mass balance were compared with area-weighted upscaled chamber fluxes from the same study area and were found to agree well within measurement uncertainty. The mass balance CH4 fluxes were found to be significantly higher than the CH4 fluxes reported by many land-surface process models compiled as part of the Global Carbon Project. There was high variability in both flux distribution and magnitude between the individual models. This further supports previous studies that suggest that land-surface models are currently ill-equipped to accurately capture carbon fluxes inthe region.This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 2)'.
Highlights
As of 2020, atmospheric abundances of the greenhouse gases methane (CH4) and carbon dioxide (CO2) have increased by approximately 1155 ppb and 132 ppm, respectively, since 1850 AD, and continue to rise at an estimated rate of 9 ppb per year for CH4 and 2 ppm per year for CO2 [1]
5.93 ± 0.72 mg m−2 h−1 was obtained for CH4, and a peak total land area-normalized flux of −513 ± 74 mg m−2 h−1 was obtained for CO2 using the aircraft mass balance flux method for this area of northern Sweden and Finland
These results indicate that the wetlands in this area are a significant net source of CH4, and the area represents a notable biospheric CO2 sink
Summary
As of 2020, atmospheric abundances of the greenhouse gases methane (CH4) and carbon dioxide (CO2) have increased by approximately 1155 ppb and 132 ppm, respectively, since 1850 AD, and continue to rise at an estimated rate of 9 ppb per year for CH4 and 2 ppm per year for CO2 [1]. The Methane Observations and Yearly Assessments (MOYA) project aimed to use in situ measurements, targeted field campaigns and modelling to constrain global CH4 sources and sinks from a variety of key CH4 emission hotspots, such as African biomass burning [34] and Tropical wetlands (Shaw et al in review). In situ measurements of CH4 fluxes in these key areas will aid in reducing the uncertainty in their contribution to the global CH4 budget and may provide a clearer explanation for currently rising atmospheric CH4 mole fractions (MFs). This work presents in situ aircraft measurements of CH4, CO2 and N2O MF during one of the survey flights carried out during the MOYA-Arctic campaign From these measurements, mass balance flux estimates for CH4 and CO2 were calculated and compared with previous similar aircraft studies in the region by O’Shea et al [33]. This study compares the fluxes obtained via aircraft mass balance with fluxes from Global Carbon Project (GCP) wetland process models, where both the magnitude and spatial distribution of CH4 fluxes are compared with the aircraft results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
