Temporal variability of CO2 and CH4 concentrations and their δ13C isotopic signatures in the atmosphere of the southern taiga zone of Western Siberia derived from observations at the Fonovaya observatory in 2022-2024
M.Yu. Arshinov, V.G. Arshinova, B.D. Belan, D.K. Davydov, A.V. Kozlov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: atmospheric composition, greenhouse gas, concentration, carbon, stable isotope, isotopic signature, southern taiga, Western Siberia
Abstract
To better understand the current trends in the growth of greenhouse gas concentrations on a regional scale, it is necessary to analyze their isotopic composition in order to identify their sources and sinks, which determine both seasonal and long-term changes in their atmospheric content. Continuous observations of atmospheric CO2 and CH4 and the carbon isotope composition of their molecules carried out in 2022-2024 at the Fonovaya observatory enabled the range of background values and seasonal pattern of δ13C-CO2 and δ13C-CH4 in the atmosphere of the southern taiga zone of Western Siberia to be determined. The average daytime (01-05 pm) values of δ13C-CO2 and δ13C-CH4 varied in the ranges -9.2 to -5.7‰ and -51.7 to -46.5‰, respectively. The analysis of background values revealed a sharp summer minimum in CO2 concentration and, conversely, a maximum in δ13C-CO2, indicating intensive uptake of 12CO2 by the regional terrestrial ecosystems. Winter values of both CO2 concentration and δ13C-CO2 are consistent with data from other greenhouse gas monitoring stations in the Northern Hemisphere. The pattern of seasonal variations in atmospheric CH4 mixing ratios and δ13C-CH4 values in the region under study indicates that the winter maximum in CH4 content is driven by anthropogenic factors, while the summer maximum, by the predominance of biogenic methane emissions from Western Siberian wetlands. Using the Keeling plot method, source/sink signatures influencing changes in atmospheric CO2 and CH4 concentrations in the area under study were determined for each month of the year. The results can be used when analyzing and interpreting long-term observations of greenhouse gases in Siberia.
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