HR: 0800h
AN: A41B-0030    [Abstracts]
TI: Oxygen Isotopic Composition of Carbon Dioxide in the Middle Atmosphere
AU: * Liang, M
EM: mcl@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Blake, G A
EM: gab@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Lewis, B R
EM: Brenton.Lewis@anu.edu.au
AF: Research School of Physical Sciences and Engineering, The Australian National University, The Australian National University, Canberra, ACT 0200 Australia
AU: Yung, Y L
EM: yly@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AB: The isotopic composition of long-lived trace gases provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 ppmv in the mesosphere. Current models consider O₃ as the main source of O(¹D) in the mesosphere, but we note that the photolysis of ¹⁶O¹⁷O and ¹⁶O¹⁸O by solar Lyman-α radiation yields O(¹D) 10-100 times more enriched in ¹⁷O and ¹⁸O than that from ozone photodissociation. We therefore incorporate both photochemical sources into stratospheric and mesospheric chemical transport models that quantitatively predict the unusual enhancement of ¹⁷O in CO₂ from the middle atmosphere. New laboratory and atmospheric measurements are proposed to test our model and validate the use of CO₂ isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. Once fully understood the `anomalous' oxygen signature in CO₂ can be used in turn to study biogeochemical cycles, in particular to constrain the gross carbon fluxes between the atmosphere and terrestrial biosphere.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 0426 Biosphere/atmosphere interactions (0315)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005