Time and space variations of the carbon isotopic ratio of tropospheric carbon dioxide over Japan

T. Nakazawa, Shinji Morimoto, Shuji Aoki, M. Tanaka

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Abstract

The amplitudes of the seasonal cycles of δ13C and CO2 concentration decreased with increasing height, with a phase delay of about one month between the lower and upper troposphere. From a comparison of the observed seasonal variation of the CO2 with that of δ13C, it was found that the rate of change in δ13C with respect to the CO2 concentration is about -0.05‰/ppmv. This suggests that the seasonal CO2 cycle over Japan is mainly produced by seasonally-dependent biospheric activities. δ13C decreased secularly at an average rate of about -0.04‰/yr, due mainly to combustion of fossil fuel with isotopically light CO2. Interannual variations of δ13C, superimposed on the long-term trend, were also observed, which were approximately opposite in phase with those of the CO2 concentration. The comparison of both interannual variations suggested that the cause could be primarily attributed to an imbalance in the CO2 exchange between the atmosphere and the biosphere rather than between the atmosphere and the oceans. -from Authors

Original languageEnglish
Pages (from-to)258-274
Number of pages17
JournalTellus, Series B
Volume45 B
Issue number3
Publication statusPublished - 1993 Jan 1

ASJC Scopus subject areas

  • Atmospheric Science

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