LONG-TERM MONITORING OF CARBON AND OXYGEN-ISOTOPE RATIOS OF STRATOSPHERIC CO2 OVER JAPAN

We have been measuring stable isotopic ratios of carbon (delta-C-13) and oxygen (delta-O-18) of carbon dioxide in the stratosphere (18-35 km altitudes) over Japan since 1985, presenting here the first temporal delta-C-13 and delta-O-18 records between 1985 and 1991. The stratospheric delta-C-13 is gradually decreasing due to anthropogenic effects with a rate of approximately -0.03 parts per thousand y-1, which is similar to the tropospheric value. The previously found O-18 enrichment in stratospheric CO2 has been maintained almost steadily during the 6 years, with a monotonous delta-O-18 increase with increasing altitude up to 35 km over Japan.