Patterns of CO₂ and radiocarbon across high northern latitudes during International Polar Year 2008

Measurements within fresh fire plumes yielded CO₂ to CO emission ratios of 4 to 16 ppmv ppmv-1 and a mean CO₂ emission factor of 1698 ± 280 g kg-1 dry matter. From the ¹ ⁴C in CO₂ content of 48 whole air samples, mean spring (46.6 ± 4.4‰) and summer (51.5 ± 5‰) Δ¹ ⁴CO₂ values indicate a 5‰ seasonal difference. Although the northern midlatitudes were identified as the emissions source regions for the majority of the spring samples, depleted Δ¹ ⁴CO₂ values were observed in <1% of the data set.

Rather, ARCTAS Δ¹ ⁴CO₂ observations (54%) revealed predominately a pattern of positive disequilibrium (1-7‰) with respect to background regardless of season owing to both heterotrophic respiration and fire-induced combustion of biomass. Anomalously enriched Δ¹ ⁴CO₂ values (101-262‰) measured in emissions from Lake Athabasca and Eurasian fires speak to biomass burning as an increasingly important contributor to the mass excess in Δ¹ ⁴CO₂ observations in a warming Arctic, representing an additional source of uncertainty in the quantification of fossil fuel CO₂.