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

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. δ¹³C of stratospheric CO₂observed over these locations enriched with increasing altitude. A negative correlation between δ¹³C and CO₂ concentration with Δδ¹³C/ΔCO₂ of −0.02‰ ppmv⁻¹ was found in the lower stratosphere. Although CO₂ concentration was almost constant in the mid-stratosphere, the δ¹³C enrichment was observed in succession. δ¹⁸O of stratospheric CO₂ also enriched with increasing altitude. The enrichment was significant; δ¹⁸O 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 δ¹⁸O 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⁻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.