Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Thonat, Thibaud, Saunois, Marielle, Bousquet, Philippe, Pison, Isabelle, Tan, Zeli, Zhuang, Qianlai, Crill, Patrick M., Thornton, Brett F., Bastviken, David, Dlugokencky, Ed J., Zimov, Nikita, Laurila, Tuomas, Hatakka, Juha, Hermansen, Ove, Worthy, Doug E. J.
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Modélisation INVerse pour les mesures atmosphériques et SATellitaires (SATINV), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ICOS-RAMCES (ICOS-RAMCES), Guangxi Institute of Meteorological Disaster-Reducing Research, Department of Physics Lancaster, Lancaster University, Department of Geological Sciences Stockholm, Stockholm University, The Department of Thematic Studies - Water and Environmental Studies, Linköping University (LIU), National Oceanic and Atmospheric Administration (NOAA), Vienna University of Technology (TU Wien), Finnish Meteorological Institute (FMI), Norsk Institutt for Luftforskning (NILU), Environment and Climate Change Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Arctic; arctic methane; Climate change
• Online Access: https://hal.archives-ouvertes.fr/hal-01584259; https://hal.archives-ouvertes.fr/hal-01584259/document; https://hal.archives-ouvertes.fr/hal-01584259/file/acp-17-8371-2017.pdf; https://doi.org/10.5194/acp-17-8371-2017

International audience Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources, in particular freshwater emissions which are often overlooked in methane modelling. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions; emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning. In particular, freshwater systems play a decisive part in summer, representing on average between 11 and 26 % of the simulated Arctic methane signal at the sites. This indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land-surface model used to prescribe wetland emissions can be critical in correctly representing methane mixing ratios. The closest agreement with the observations is reached when using the two wetland models which have emissions peaking in August–September, while all others reach their maximum in June–July. Such phasing provides an interesting constraint on wetland models which still have large uncertainties at present. Also testing different freshwater emission ...