Atmospheric CO2, d(O2/N2), APO and oxidative ratios from aircraft flask samples over Fyodorovskoye, Western Russia

We present atmospheric CO2 and d(O2/N2) from flask samples taken on board aircraft over Fyodorovskoye (56°27'N, 32°55'E) at heights of 3000 m and 100 m between 1998 and 2008. The long-term trends for CO2 and d(O2/N2) are similar for both sampling heights, and also similar to observations from marine background station Mace Head (Ireland) and coastal station Lutjewad (the Netherlands). The seasonal CO2 amplitude at 100 m was almost twice as large as at 3000 m and a phase shift in the seasonality of about two weeks between both sampling heights was observed. This indicates a dominant influence on CO2 in the boundary layer from the regional biosphere which is confirmed by analysis of the d(O2/N2) to CO2 oxidative ratio (OR). Together with simulations with the TM3 model, our data suggest that the observed OR of -1.7 ± 0.2 in the free troposphere is mainly driven by exchange processes with the ocean. Within the boundary layer an OR of -0.89 ± 0.12 was observed which supports the results of other recent studies suggesting the commonly used value of -1.1 for biospheric OR is likely too low.