Long-term observation of mass-independent oxygen isotope anomaly in stratospheric CO 2

• Main Authors: Kawagucci, S., Tsunogai, U., Kudo, S., Nakagawa, F., Honda, H., Aoki, S., Nakazawa, T., Tsutsumi, M., Gamo, T.
• Other Authors: Department of Earth and Planetary Sciences Sapporo, Hokkaido University Sapporo, Japan, Department of Chemical Oceanography, Ocean Research Institute, Japan Aerospace Exploration Agency Sagamihara (JAXA), Center for Atmospheric and Oceanic Studies Sendai, Tohoku University Sendai
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Kiruna
• Online Access: https://hal.science/hal-00303168; https://hal.science/hal-00303168/document; https://hal.science/hal-00303168/file/acpd-7-15723-2007.pdf

International audience Anomalous oxygen isotopic compositions of stratospheric CO 2 were first reported in 1989, although their detailed behavior in the middle atmosphere is still open question. We collected 60 stratospheric air samples over Sanriku, Japan from 1991 to 2004 and Kiruna, Sweden in 1997. Using these accumulated air samples, we performed long-term observations of triple oxygen isotope compositions of stratospheric CO 2 . It is the first simultaneous observation in the stratosphere of both relations between ? 17 O CO2 and [N 2 O], and ? 18 O CO2 and ? 17 O CO2 , accurately. Observations confirmed simultaneous linear correlations between ? 18 O CO2 , ? 17 O CO2 , and [N 2 O] within [N 2 O]>50 ppbv: the correlations faded away along with decreasing [N 2 O] from 50 ppbv. For dividing observation results by [N 2 O]=50 ppbv, the divided datasets show that 1) both ? 17 O CO2 and ? 18 O CO2 are conservative parameters within the N 2 O-rich division, 2) the slope of least squares regression on ? 18 O?? 17 O plot for the N 2 O-rich division is significantly steeper than that of the N 2 O-depleted one, and 3) the N 2 O-depleted division shows a discrepancy with recent model calculations, suggesting unconsidered isotope fractionation processes on complicated oxygen interactions in the CO 2 -O 3 -O 2 system in the upper stratosphere and mesosphere.