Carbon dioxide variations in the stratosphere over Japan, Scandinavia and Antarctica

Systematic collections of stratospheric air samples have been conducted over Japan since 1985 using a balloon-borne cryogenic sampler. The collection of stratospheric air samples was also carried out twice over Scandinavia and once over Antarctica. Vertical profiles of CO2 concentration thus obtained over these locations were quite similar to each other; CO2 concentration decreased with increasing altitude in the lower stratosphere and reached an almost constant value in the mid-stratosphere. 13C of stratospheric CO2 observed over these locations enriched with increasing altitude. A negative correlation between 13C and CO2 concentration with 13C/CO2 of 0.02 ppm was found in the lower stratosphere. Although CO2 concentration was almost constant in the mid-stratosphere, the 13C enrichment was observed in succession. 18O of stratospheric CO2 also enriched with increasing altitude. The enrichment was significant; 18O was almost 0 at the tropopause and reached a maximum value of about 11 at a layer with N2O concentration of about 10 ppbv. A compact relation between 18O and N2O concentration was consistently observed for these locations. Stratosperic CO2 over Japan showed a secular increase with an average rate of 1.4 ppmv/yr for the period 1985-2000. The secular increase was not constant with time, and temporal stagnation of the CO2 increase was observed in 1997