Correlations among atmospheric CO2, CH4 and CO in the Arctic, March 1989

During six aircraft flights conducted as part of the third Arctic Gas and Aerosol Sampling Program (AGASP III, March 1989), 189 air samples were collected throughout the Arctic troposphere and lower stratosphere for analysis of CO₂, CH₄ and CO. The mixing ratios of the three gases varied significantly both horizontally and vertically. Elevated concentrations were found in layers with high anthropogenic aerosol concentrations (Arctic Haze). The mixing ratios of CO₂, CH₄ and CO were highly correlated on all flights. A linear regression of CH₄ vs CO₂ for pooled data from all flights yielded a correlation coefficient (r²) of 0.88 and a slope of 13.5 ppb CH₄/ppm CO₂ (n = 186). For CO vs CO₂ a pooled linear regression gave r² = 0.91 and a slope of 15.8 ppb CO/ppm CO₂ (n = 182). Carbon dioxide, CH₄ and CO also exhibited mean vertical gradients with slopes of 0.37, –4.4 and −4.2 ppb km⁻¹, respectively.

Since the carbon dioxide variations observed in the Arctic atmosphere during winter are due primarily to variations in the emissions and transport of anthropogenic CO₂ from Europe and Asia, the strong correlations that we have found suggest that a similar interpretation applies to CH₄ and CO. Using reliable estimates of CO₂ emissions for the source regions and the measured CH₄/CO₂ and CO/CO₂ ratios, we estimate a regional European CH₄ source of 47±6 Tg CH₄ yr⁻¹ that may be associated with fossil fuel combustion. A similar calculation for CO results in an estimated regional CO source of 82±2 Tg CO yr⁻¹.