Vertical profiles of the O 2 /N 2 ratio in the stratosphere over Japan and Antarctica

To examine the spatial and temporal behavior of stratospheric O 2 , air samples were collected using a cryogenic sampler over Sanriku, Japan and Syowa, Antarctica and analyzed for δ(O 2 /N 2 ), δ 15 N of N 2 and δ 18 O of O 2 . The measured values of all these components decreased gradually with height. The differences in δ(O 2 /N 2 ), δ 15 N and δ 18 O between the middle and lowermost levels of the stratosphere were about 250, 100, and 180 per meg, respectively. The observed stratospheric profiles of δ 15 N and δ 18 O were in agreement with those calculated using a steady‐state 1‐dimensional eddy‐diffusion/molecular‐diffusion model, which suggests that the upward decrease of stratospheric δ(O 2 /N 2 ) is caused by a gravitational separation of O 2 and N 2 molecules. The averaged stratospheric δ(O 2 /N 2 ) at heights above 20–25 km over Sanriku, corrected for the gravitational separation, was always higher than the upper tropospheric δ(O 2 /N 2 ) value over Japan, and it decreased secularly. From the past temporal δ(O 2 /N 2 ) variation deduced from the gravitational separation‐corrected stratospheric δ(O 2 /N 2 ) values and the mean ages of the respective air samples, which corresponds to its secular trend in the troposphere, average terrestrial biospheric and oceanic CO 2 uptake for October 1993–September 2001 were estimated to be 1.1 ± 1.3 and 1.8 ± 1.3 GtC yr −1 , respectively.