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abstract Temporal variations of δ13 C of atmospheric CO2 in the past have been reconstructed from the δ13 C values of CO2 observed in firn at Dome Fuji, Antarctica. The effective diffusivities of CO2 in firn were estimated for Dome Fuji and another Antarctic site, H72. The age distributions of 13 CO2 in firn were first calculated by using a one-dimensional diffusion model, and then the past values of the atmospheric δ13 C were derived by using an iterative procedure so that the calculated and observed vertical profiles of δ13 C of CO2 in firn agreed with each other. This reconstruction method was also applied to the CH4 concentration to confirm its validity. The values of the atmospheric δ13 C thus estimated were in good agreement with those from direct atmospheric measurements at Syowa Station, Antarctica, even for the levelling off of the secular decrease observed in the first half of the 1990s. The statistical uncertainty of the iterative procedure was examined by adding normal pseudo-random numbers to the observed δ13 C values in firn. We also calculated the δ13 C values for firn at H72 using the reconstructed history of the atmospheric δ13 C, and its vertical profile was found to be in close agreement with the observational result. [ABSTRACT FROM AUTHOR]

abstract 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. δ13 C of stratospheric CO2 observed over these locations enriched with increasing altitude. A negative correlation between δ13 C and CO2 concentration with Δδ13 C/ΔCO2 of -0.02‰ ppmv-1 was found in the lower stratosphere. Although CO2 concentration was almost constant in the mid-stratosphere, the δ13 C enrichment was observed in succession. δ18 O of stratospheric CO2 also enriched with increasing altitude. The enrichment was significant; δ18 O was almost 0‰ at the tropopause and reached a maximum value of about 11‰ at a layer with N2 O concentration of about 10 ppbv. A compact relation between δ18 O and N2 O concentration was consistently observed for these locations. Stratosperic CO2 over Japan showed a secular increase with an average rate of 1.4 ppmv yr-1 for the period 1985–2000. The secular increase was not constant with time, and temporal stagnation of the CO2 increase was observed in 1997. [ABSTRACT FROM AUTHOR]