Atmospheric methane concentration and fluxes on western part of Arctic Eurasian shelf in late autumn 2023: shipborne observations and model simulation
Yu.A. Shtabkin1, K.B. Moiseenko1, I.B. Belikov1, V.A. Belousov1, A.V. Vasileva1, N.S. Kirillova1, D.A. Pestunov2, B.D. Belan2, M.D. Kravchishina3
1Federal state budgetary scientific institution Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences, Moscow, Russia
2V.E. Zuev Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
3Shirshov Institute of Oceanology of Russian Academy of Sciences, Moscow, Russia
Keywords: atmospheric composition, shipborne measurements, Arctic, methane emission, backward trajectory, model simulation, numerical assessment
Abstract
Quantifying methane emissions from Arctic shelf seas is one of the most poorly studied issues of global greenhouse gas budget, largely due to the sparse observational network at high latitudes. This paper presents the results of continuous shipborne measurements of near-surface CH4 and CO2 concentrations in Kara and Barents Seas during the 93rd cruise of the scientific research vessel Akademik Mstislav Keldysh (8 November - 7 December 2023). For episodes of high methane mixing ratios (> 2050 ppb), backward trajectories of air masses were calculated, and in situ data were compared with simulations using the regional WRF-Chem model. This approach enabled spatial localization of emission sources and assessment of methane fluxes at water - atmosphere interface. The highest emissions, with median and peak values of 55.5 and 363 mg/(m2 h), respectively, and a near-surface concentration of up to 2118 ppb, were found in southwestern Kara Sea (Baydaratskaya Bay), in good qualitative agreement with floating chamber flux measurements (86.4 and 483 mg/(m2 h)). These values are comparable to or exceed wintertime methane fluxes from tundra and wetland ecosystems in Western Siberia (40-270 mg/(m2 h)), thus pointing out to the potentially significant contribution of shelf emissions to regional atmospheric methane budget. The proposed approach for retrieving fluxes from near-surface concentration data can be applied to regionalization of point measurements and refining flux estimates in other Arctic areas where observational data are limited.
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