Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements
Thibaud Thonat1, Marielle Saunois1, Philippe Bousquet1, Isabelle Pison1, Zeli Tan2, Qianlai Zhuang3, Patrick Crill4, Brett Thornton4, David Bastviken5, Ed J. Dlugokencky6, Nikita Zimov7, Tuomas Laurila8, Juha Hatakka9, Ove Hermansen9, and Doug E. J. Worthy101Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRSUVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France 2Pacific Northwest National Laboratory, Richland, Washington, USA 3Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA 4Department of Geological Sciences and Bolin Centre for Climate Research, Svante Arrhenius väg 8, 106 91, Stockholm, Sweden 5Department of Thematic Studies – Environmental Change, Linköping University, 581 83 Linköping, Sweden 6NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, Colorado, USA 7Northeast Science Station, Cherskiy, Russia 8Climate and Global Change Research, Finnish Meteorological Institute, Helsinki, Finland 9NILU − Norwegian Institute for Air Research, Kjeller, Norway 10Environment Canada, Toronto, Ontario, Canada
Received: 24 Feb 2017 – Accepted for review: 07 Mar 2017 – Discussion started: 09 Mar 2017
Abstract. 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. 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; 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 concentrations. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric CH4. The study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.
Thonat, T., Saunois, M., Bousquet, P., Pison, I., Tan, Z., Zhuang, Q., Crill, P., Thornton, B., Bastviken, D., Dlugokencky, E. J., Zimov, N., Laurila, T., Hatakka, J., Hermansen, O., and Worthy, D. E. J.: Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-169, in review, 2017.