Long-term observation of mass-independent oxygen isotope anomaly in stratospheric CO<sub>2</sub>

Abstract

Stratospheric and upper tropospheric air samples were collected during 1994-2004 over Sanriku, Japan and in 1997 over Kiruna, Sweden. Using these archived air samples , we determined the triple oxygen-isotope composition of stratospheric CO 2 and the N 2 O mixing ratio. The maximum 17 O CO 2 value of +12.2‰, resembling that observed previously in the mesosphere at 60 km height, was found in the middle stratosphere over Kiruna at 25.6 km height, suggesting that upper stratospheric and mesospheric air descended to the middle stratosphere through strong downward advection. A least-squares regression analysis of our observations on a δ 18 O CO 2-δ 17 O CO 2 plot (r 2 >0.95) shows a slope of 1.63±0.10, which is similar to the reported value of 1.71±0.06, thereby confirming the linearity of three isotope correlation with the slope of 1.6-1.7 in the mid-latitude lower and middle stratosphere. The slope decrease with increasing altitude and a curvy trend in three-isotope correlation reported from previous studies were not statistically significant. Using negative linear correlations of 17 O CO 2 and δ 18 O CO 2 with the N 2 O mixing ratio, we quantified triple oxygen-isotope fluxes of CO 2 to the troposphere as +48‰ GtC/yr (17 O CO 2) and +38‰ GtC/yr (δ 18 O CO 2) with ∼30% uncertainty. Comparing recent model results and observations , underestimation of the three isotope slope and the maximum 17 O CO 2 value in the model were clarified, suggesting a smaller O 2 photolysis contribution than that of the model. Simultaneous observations of δ 18 O CO 2 , δ 17 O CO 2 , and N 2 O mixing ratios can elucidate triple oxygen isotopes in CO 2 and clarify complex interactions among physical, chemical , and photochemical processes occurring in the middle atmosphere.

Global 3‐D Simulations of the Triple Oxygen Isotope Signature Δ17O in Atmospheric CO2

“…Experimental data sets for stratospheric N 2 O and Δ 17 O in CO 2 from Thiemens et al (), Boering et al (), Kawagucci et al (), and Wiegel et al () were examined to test the robustness of the N 2 O–Δ 17 O(CO 2 ) correlation. The Δ 17 O values for these studies were recalculated from the reported δ 17 O and δ 18 O signatures using the definition of Δ 17 O as given in equation .…”

“…Overview of simulated and measured stratospheric N 2 O mole fraction and Δ 17 O signature in CO 2 . (a) Annual mean, zonal mean TM5 model predictions of detrended N 2 O mole fractions using a horizontal resolution of 6° × 4° and 25 vertical levels compared to detrended measurements of N 2 O mole fractions from Thiemens et al (), Boering et al (), Kawagucci et al (), and Wiegel et al () for stratospheric air in Northern Hemisphere. The background color indicates the value of the TM5 model prediction, and the color of the symbols indicates the measured value.…”

“…Stratospheric CO 2 was shown to be anomalously enriched in oxygen isotopes with Δ 17 O≫ 0‰ in measurement campaigns performed with rockets (Thiemens et al, ), aircraft (Boering et al, ; Thiemens et al, ), balloons (Alexander et al, ; Kawagucci et al, ; Lämmerzahl et al, ; Mrozek et al, ), or using aircraft and balloons (Wiegel et al, ; Yeung et al, ). The anomalous isotopic composition of stratospheric CO 2 has been linked to oxygen exchange with stratospheric O 3 , which has a positive Δ 17 O signature, by Yung et al ().…”

Determination of the triple oxygen and carbon isotopic composition of CO2 from atomic ion fragments formed in the ion source of the 253 Ultra high‐resolution isotope ratio mass spectrometer

“…Since the discovery of mass‐independent fractionation, the Δ 17 O value has been used to study sources/sinks of atmospheric trace gases and chemical reaction pathways. Several studies have shown that CO 2 acquires Δ 17 O from O 3 via photochemical isotope exchange in the stratosphere . When this CO 2 re‐enters the troposphere the Δ 17 O is successively reduced by oxygen isotope exchange with leaf, soil and ocean water.…”

Triple Oxygen and Clumped Isotope Compositions of CO2 in the Middle Troposphere

“…(A) Oxygen isotope plot for CO 2 from the present work (red symbol) based on CARIBIC samples collected at altitude ~10 km and earlier measurements made in the stratosphere/mesosphere (Alexander et al, ; Kawagucci et al, ; Lammerzahl et al, ; Thiemens, Jackson, & Brenninkmeijer, ; Thiemens, Jackson, Zipf, et al, ; Yeung et al, ; Zipf & Erdman, ) and at the surface (Liang, Mahata, Laskar, Thiemens, et al, ; Thiemens et al, ). (B) Δ 17 O vs δ 18 O plot for the present study is compared with the model (Liang et al, ) as well as available studies in the stratosphere (in insets parts of the plots around the data points are zoomed in for better comparison).…”