Vol. 39, issue 05, article # 11

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.

Keywords:

atmospheric composition, greenhouse gas, concentration, carbon, stable isotope, isotopic signature, southern taiga, Western Siberia

Figures:

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