Variations of the carbon and oxygen isotopic ratios of atmospheric CO2 at Syowa Station, Antarctica

• Main Authors: Shohei Murayama, Takakiyo Nakazawa, Shuhji Aoki, Shinji Morimoto
• Format: Article in Journal/Newspaper
• Language: English; Japanese
• Published: National Institute of Polar Research 1997
• Subjects: Geography (General); G1-922; Syowa Station; Antarc*; Antarctica
• Online Access: https://doi.org/10.15094/00008968; https://doaj.org/article/d66176f6839b40a89280baf23e1a5b2e

Measurements of stable isotopic ratios of atmospheric CO_2 have been made at Syowa Station, Antarctica since 1986. The average peak-to-peak amplitude of the seasonal cycle of δ^<13>C was about 0.04‰ with the maximum in autumn and the minimum in spring. From comparison with the seasonal cycle of the CO_2 concentration, it was speculated that air with high CO_2 concentration influenced by exchange between the atmosphere and the biosphere and/or combustion of fossil fuel arrives at the station from late fall to early spring, while oceanic origin air with low CO_2 is transported from late spring to summer. The average increase rate of δ^<13>C of atmospheric CO_2 between 1986 and 1990 was about -0.02‰/year. Interannual variations of δ^<13>C, superimposed on the long-term trend, were also seen. These were approximately opposite in phase to those of the CO_2 concentration. The comparison of both interannual variations suggests that the principal cause could be an imbalance in the CO_2 exchange between the atmosphere and the biosphere. On the other hand, δ^<18>O of atmospheric CO_2 showed a clear seasonal cycle with the maximum in summer and minimum in winter, which may also be related to the seasonally-dependent atmospheric transport.