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UP: Umweltphysik

UP 25: Atmosph
ärische Spurengase und Aerosole: Laboruntersuchungen

UP 25.1: Fachvortrag

Mittwoch, 15. März 2006, 12:00–12:15, E

Understanding the isotopic composition of stratospheric CO₂ — •Christof Janssen¹, Béla Tuzson¹, Robina Shaheen¹, and Thomas Roeckmann² — ¹Max-Planck-Institut für Kernphysik, Heidelberg — ²University of Utrecht, Netherlands

Stratospheric CO₂ shows a pronounced oxygen isotopic composition that forms a linear array in a three isotope plot, where the heavy oxygen isotopes are correlated according to δ ¹⁷O∼ 1.7  δ¹⁸O. The preferential enrichment of ¹⁷O is thought to be due to isotope transfer from stratospheric ozone, which is well known for its extraordinary enrichment in the oxygen isotopes. Recently, a marker of past biospheric productivity has been suggested that is based on this particular isotope transfer mechanism. However, present modeling and laboratory simulation attempts either miss important features of the stratospheric setting or are not able to reproduce the atmospheric observation.

Here, we present laboratory measurements of CO₂ and ozone that are based on mass spectrometric and laser spectroscopic techniques. Our results pose important kinetic constraints on the transfer process. The measurements indicate that a variety of factors contribute to the stratospheric observations and provide a first clue to the understanding of the kinetic details of the isotope transfer from ozone into CO₂.