Recent Trends in Stratospheric Chlorine From Very Short-Lived Substances

Ryan Hossaini*, Elliot Atlas, Sandip S. Dhomse, Martyn P. Chipperfield, Peter F. Bernath, Anton M. Fernando, Jens Mühle, Amber A. Leeson, Stephen A. Montzka, Wuhu Feng, Jeremy J. Harrison, Paul Krummel, Martin K. Vollmer, Stefan Reimann, Simon O'Doherty, Dickon Young, Michela Maione, Jgor Arduini, Chris R. Lunder

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

7 Citations (Scopus)
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Abstract

Very short-lived substances (VSLS), including dichloromethane (CH 2 Cl 2 ), chloroform (CHCl 3 ), perchloroethylene (C 2 Cl 4 ), and 1,2-dichloroethane (C 2 H 4 Cl 2 ), are a stratospheric chlorine source and therefore contribute to ozone depletion. We quantify stratospheric chlorine trends from these VSLS (VSLCl tot ) using a chemical transport model and atmospheric measurements, including novel high-altitude aircraft data from the NASA VIRGAS (2015) and POSIDON (2016) missions. We estimate VSLCl tot increased from 69 (±14) parts per trillion (ppt) Cl in 2000 to 111 (±22) ppt Cl in 2017, with >80% delivered to the stratosphere through source gas injection, and the remainder from product gases. The modeled evolution of chlorine source gas injection agrees well with historical aircraft data, which corroborate reported surface CH 2 Cl 2 increases since the mid-2000s. The relative contribution of VSLS to total stratospheric chlorine increased from ~2% in 2000 to ~3.4% in 2017, reflecting both VSLS growth and decreases in long-lived halocarbons. We derive a mean VSLCl tot growth rate of 3.8 (±0.3) ppt Cl/year between 2004 and 2017, though year-to-year growth rates are variable and were small or negative in the period 2015–2017. Whether this is a transient effect, or longer-term stabilization, requires monitoring. In the upper stratosphere, the modeled rate of HCl decline (2004–2017) is −5.2% per decade with VSLS included, in good agreement to ACE satellite data (−4.8% per decade), and 15% slower than a model simulation without VSLS. Thus, VSLS have offset a portion of stratospheric chlorine reductions since the mid-2000s.

Original languageEnglish
JournalJournal of Geophysical Research: Atmospheres
Early online date18 Jan 2019
DOIs
Publication statusE-pub ahead of print - 18 Jan 2019

Keywords

  • chlorine
  • chloroform
  • dichloromethane
  • ozone
  • stratosphere
  • VSLS

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    Hossaini, R., Atlas, E., Dhomse, S. S., Chipperfield, M. P., Bernath, P. F., Fernando, A. M., Mühle, J., Leeson, A. A., Montzka, S. A., Feng, W., Harrison, J. J., Krummel, P., Vollmer, M. K., Reimann, S., O'Doherty, S., Young, D., Maione, M., Arduini, J., & Lunder, C. R. (2019). Recent Trends in Stratospheric Chlorine From Very Short-Lived Substances. Journal of Geophysical Research: Atmospheres. https://doi.org/10.1029/2018JD029400