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 (r(2)) of 0.88 and a slope of 13.5 ppb CH4/ppm CO2 (n = 186). For CO vs CO2 a pooled linear regression gave r(2) = 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+/- 2Tg CO yr(-1).