Abstract. To understand Korea's carbon dioxide (CO2) emissions and sinks as well as those of the surrounding region, we used 70 flask-air samples collected during May 2014 to August 2016 at Anmyeondo (AMY, 36.53° N, 126.32° E; 46 m a.s.l.) World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) station, located on the west coast of South Korea, for analysis of observed 14C in atmospheric CO2 as a tracer of fossil fuel CO2 contribution (Cff). Observed 14C / C ratios in CO2 at AMY varied from −59.5 to 23.1 ‰ with the measurement uncertainty of ±1.8 ‰. The derived mean value Cff of (9.7 ± 7.8) μmol mol−1 (1σ) is greater than that found in earlier observations from Tae-Ahn Peninsula (TAP, 36.73° N, 126.13° E, 20 m a.s.l., 24 km away from AMY) of (4.4 ± 5.7) μmol mol−1 from 2004 to 2010. The enhancement above background of sulfur hexafluoride (Δx(SF6)) and carbon monoxide (Δx(CO)) correlate strongly with Cff (r > 0.7) and appear to be good proxies for fossil fuel CO2 at regional and continental scales. Samples originating from the Asian continent had greater Δx(CO) : Cff (RCO) values, (29 ± 8) to (36 ± 2) nmol μmol−1, than in Korean local air ((8 ± 2) nmol μmol−1). Air masses originating in China showed (1.8 ± 0.2) times greater RCO than a bottom-up inventory suggesting that China's CO emissions are underestimated in the inventory. However, both RCO derived from inventories and observations have decreased relative to previous studies, indicating that combustion efficiency is increasing in both China and South Korea.;
