31 Jan 2022
31 Jan 2022
Status: this preprint is currently under review for the journal ACP.

Modelling the atmospheric 34S-sulfur budget in a column model under volcanically quiescent conditions

Juhi Nagori1, Narcisa Nechita-Bândă1, Sebastian Oscar Danielache2,3, Masumi Shinkai2, Thomas Röckmann1, and Maarten Krol1,4 Juhi Nagori et al.
  • 1Institute of Marine and Atmospheric Research, University of Utrecht, Utrecht, The Netherlands
  • 2Department of Material and Life Sciences, Faculty of Science & Technology, Sophia University
  • 3Earth and Life Sciences Institute, Tokyo Institute of Technology
  • 4Meteorology and Air Quality, Wageningen University, Wageningen, The Netherlands

Abstract. We investigated the sulfur isotope budget of atmospheric carbonyl sulfide (COS) and the role of COS as a precursor for stratospheric sulfate aerosols (SSA). Currently, the sulfur isotopic budgets for both SSA and tropospheric COS are unresolved. Moreover, there is some debate on the significance of COS on SSA formation. With the use of an atmospheric column model, we model the isotopic composition of COS to resolve some of the uncertainties in its budget. We attempt to constrain the isotopic budget (32S and 34S) of COS in the troposphere and the stratosphere. We are able to constrain the model results to match the observed COS isotopic signature at the surface, which has recently been measured to lie between δ34S = 10–14 permil (‰). When we propagate this composition to SSA, we match the isotopic signal of SSA that was measured in volcanically quiescent times at 18 km as δ34S = 2.6 ‰. Our results show that COS becomes isotopically enriched during destruction in the stratosphere, and this enriched isotopic signal of COS propagates through SO2 to sulfate, creating strong positive isotopic gradients of both SO2 and sulfate in the lower stratosphere. Sensitivity tests indicate that the enriched sulfur in the stratosphere is mostly sensitive to COS photolysis, and to a lesser extent to biosphere uptake and COS emission signature. A better quantification of these processes could further support the role of COS in sustaining the SSA layer. Hence, there is a need for isotopic measurements for both stratospheric COS and SSA to better constrain these contributions.

Juhi Nagori et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-68', Marc von Hobe, 24 Feb 2022
  • RC2: 'Comment on acp-2022-68, approach not suitable to obtain new findings', Anonymous Referee #2, 07 Mar 2022
  • AC3: 'Comment on acp-2022-68', Juhi Nagori, 13 May 2022

Juhi Nagori et al.

Juhi Nagori et al.


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Short summary
The sulfur isotopes (32S and 34S) were studied to understand the sources, sinks and processes of carbonyl sulphide (COS) in the atmosphere. COS is an important source of sulfur aerosol in the stratosphere (SSA). Few measurements of COS and SSA exist, but with our 1D model, we were able to match them and show the importance of COS to sulfate formation. Moreover, we are able to highlight some important processes for the COS budget and where measurements may fill a gap in current knowledge.