Atmospheric composition study based on ship measurements in the Russian Arctic seas in summer 2019

We present observation results of methane (CH₄), its isotopic signature (δ¹³C^CH4) and carbon dioxide (CO₂) surface concentrations, made aboard the research vessel (R/V) “Akademik Mstislav Keldysh” in the Russian Arctic seas in summer 2019. The main goal of the study is to determine the possible sources of methane. As a result of the study, localized areas with an increased methane concentration (up to 2092 ppb) in the surface layer are identified. It may be related to the advection of water masses rich in organic matter from the Ob and Yenisei Rivers. In addition, increased methane concentrations (up to 2010 ppb) are observed in the Kara Sea near the Yamal Peninsula, where gas deposits are concentrated, and active methane emissions from wetland ecosystems are noted. We conclude that the average concentration of methane in surface air in the Arctic seas is determined mainly by large-scale transport of air masses.