The impact of anthropogenic chlorine emissions, stratospheric ozone change and chemical feedbacks on stratospheric water

T. Röckmann (1) , J.-U. Grooss (2) , R. Müller (2)

1 MPIK - Max-Planck-Institut für Kernphysik
2 Institut für Chemie und Dynamik der Geosphäre

Mixing ratios of water (H₂O) in the stratosphere appear to increase due to increased input of H₂O and methane from the troposphere and due to intensified oxidation of CH₄ in the stratosphere, but many of the underlying mechanisms are not yet understood. Here we identify and quantify three chemical mechanisms which must have led to more efficient oxidation of CH₄ in the stratosphere over the past several decades: 1) The increase in stratospheric chlorine levels due to anthropogenic CFC emissions, 2) the thinning of the stratospheric ozone column and 3) enhanced OH levels in the stratosphere due to increasing H₂O levels themselves. In combination with the increase in tropospheric CH₄ mixing ratios and with solar cycle related variations of upper stratospheric ozone, these effects can explain about 50% of the additional conversion of CH₄ to H₂O as observed throughout the stratosphere. The relative contributions from the individual processes have varied over the past decades.

Domaines: Océan, Atmosphère

T. Röckmann, J.-U. Grooss, R. Müller. The impact of anthropogenic chlorine emissions, stratospheric ozone change and chemical feedbacks on stratospheric water. Atmospheric Chemistry and Physics, 2004, 4 (3), pp.693-699. ⟨hal-00295432⟩