Seasonal cycle of C¹⁶O¹⁶O, C¹⁶O¹⁷O, and C¹⁶O¹⁸O in the middle atmosphere: Implications for mesospheric dynamics and biogeochemical sources and sinks of CO₂

Abstract

Here we present a two-dimensional simulation of the isotopic composition of CO 2 from the surface to an altitude of $130 km that adequately reproduce the observed seasonal cycle of CO 2 in the upper troposphere and the age of air in the stratosphere. Our model results suggest that stratospheric-tropospheric exchange not only modifies the level of heavy CO 2 in the troposphere, but also influences its seasonal cycle. Thus the isotopic composition of CO 2 in the troposphere/biosphere could be affected by the downwelling air from the stratosphere. The predicted size of the effect is detectable by current instrumentation. Implications for the use of the isotopic composition of CO 2 to constrain the gross carbon flux between the atmosphere and terrestrial biosphere and the dynamics in the remote mesosphere are discussed. O in the middle atmosphere: Implications for mesospheric dynamics and biogeochemical sources and sinks of CO 2 ,

Near Surface CO2 Triple Oxygen Isotope Composition

“…The elevated anomaly compares well with the average value found in 10 years of measurements made at La Jolla, CA, USA (Thiemens et al 2014). Liang et al (2008a) extended this model and suggested that the stratospheric-tropospheric exchange modifies the isotopic composition of CO 2 , and also influences its seasonal cycle. The results from a phase correlation study of O 3 and CO supported this conclusion and suggested that the stratosphere-troposphere exchange carries stratospheric air into the troposphere at select places (Liang et al 2008b).…”

“…MIF in stratospheric ozone (Mauersberger 1981;Thiemens et al 1991) is thought to be partially transferred into carbon dioxide (Thiemens et al 1995;Hoag et al 2005;Liang et al 2007Liang et al , 2008a (Thiemens et al 1991;Yung et al 1997;Lämmerzahl et al 2002;Boering et al 2004). Note that the photochemical processes involving O 2 , O 3 , and CO 2 introduce the positive anomaly in CO 2 and also a small corresponding negative anomaly in O 2 .…”

“…Based on the above considerations, various calculations have been performed to investigate the stratospheric CO 2 contribution to tropospheric/biospheric CO 2 . For example, a two-box model has (Cuntz et al 2003;Boering et al 2004;Hoag et al 2005;IPCC 2007;Liang et al 2008a;Wingate et al 2009;Beer et al 2010;Welp et al 2011 O anomaly is ~0.15‰ above that originating from the biosphere and hydrosphere. The elevated anomaly compares well with the average value found in 10 years of measurements made at La Jolla, CA, USA (Thiemens et al 2014).…”

Large and unexpected enrichment in stratospheric 16 O 13 C 18 O and its meridional variation

“…Stratospheric oxygen isotope covariations in CO 2 (8,11,12) consistently differ from those found in laboratory experiments simulating stratospheric photochemistry (6,(13)(14)(15)(16) Table 1). The stratospheric samples display ⌬ 47 values both higher and more variable than those exhibited by tropospheric air at the surface, which has an average ⌬ 47 value of 0.92 Ϯ 0.01‰ in remote regions (Cape Grim, Tasmania and Barrow, Alaska) (18).…”

“…In the stratosphere, the oxygen isotopic composition of CO 2 is thought to be modified by oxygen isotope exchange reactions with O( 1 D) generated by ozone photolysis (2), whereas in the troposphere it is controlled by isotope exchange reactions with liquid water in the oceans, soils, and plant leaves (3). The interplay between stratospheric and tropospheric isotope exchange reactions, in principle, could allow the relative abundances of 12 (4,5), but the stratospheric CO 2 photochemical system is still underconstrained, and our understanding of it is incomplete.…”