Comprehensive (Shipborne and Aircraft) Measurements of Atmospheric Concentrations of Methane and Carbon Dioxide in the Arctic in September 2022

The article presents the results of in situ measurements of the concentration of methane (CH4), value of δ13C-СН4, and concentration of carbon dioxide (CO2) in atmospheric air above the sea surface at the height of ~19 m, collected on board the R/V Akademik Mstislav Keldysh in the southern Kara and Barents seas, obtained in September 2022. For the first time in the Russian Arctic, data of marine investigations were compared with vertical profiles of CH4 and CO2 concentrations in the atmospheric air layer from 200 to 9000 m, obtained in September 9–10, 2022, during synchronous measurements on board the research vessel and the Optik Tu-134 aircraft laboratory (unique scientific facility Aircraft Laboratory Tu-134 Optik) in the Kara Sea. An increase (by ~10 ppb) in the CH4 concentration in the atmospheric layer above the sea surface was revealed in the southern Kara Sea, which is most likely associated with the discharge of methane-containing fluids from sediment strata. A dependence of CH4 concentration on the direction of air masses advection was clearly indicated throughout our studies. With advection of air from the north, the CH4 concentration tends to the background value (~1990 ppb) for the Arctic. The CH4 concentration increases to 2060–2070 ppb when air arrives from the south, i.e., from the continental regions of European Russia and Kazakhstan. Local episodes of increased CH4 concentration in the air above the sea surface were identified in the area of jet-bubble CH4 discharge from sediments of Baydaratskaya Bay, apparently associated with cold seep activity.