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Low-volatility vapors and new particle formation over the Southern Ocean during the Antarctic Circumnavigation Expedition
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  • Andrea Baccarini,
  • Josef Dommen,
  • Katrianne Lehtipalo,
  • Silvia Henning,
  • Robin L Modini,
  • Martin Gysel-Beer,
  • U. Baltensperger,
  • Julia Schmale
Andrea Baccarini
École polytechnique fédérale de Lausanne ‐ EPFL
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Josef Dommen
Paul Scherrer Institute
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Katrianne Lehtipalo
University of Helsinki
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Silvia Henning
Institute for Tropospheric Research
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Robin L Modini
Paul Scherrer Institute
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Martin Gysel-Beer
Paul Scherrer Institute
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U. Baltensperger
Paul Scherrer Institute
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Julia Schmale
École Polytechnique Fédérale de Lausanne

Corresponding Author:[email protected]

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Abstract

During summer, the Southern Ocean is largely unaffected by anthropogenic emissions, which makes this region an ideal place to investigate marine natural aerosol sources and processes. A better understanding of natural aerosol is key to constrain the preindustrial aerosol state and reduce the aerosol radiative forcing uncertainty in global climate models. We report the concentrations of gaseous sulfuric acid, iodic acid, and methanesulfonic acid (MSA) together with a characterization of new particle formation (NPF) events over a large stretch of the Southern Ocean. Measurements were conducted on board the Russian icebreaker Akademik Tryoshnikov from January to March 2017. Iodic acid is characterized by a particular diurnal cycle with reduced concentration around noon, suggesting a lower formation yield when solar irradiance is higher. Gaseous MSA does not have a diurnal cycle and measured concentrations in gas and condensed phase are compatible with this species being primarily produced via heterogeneous oxidation of dimethyl sulfide and subsequent partitioning into the gas phase. We also found that NPF in the boundary layer is mainly driven by sulfuric acid but it occurred very rarely over the vast geographical area probed and did not contribute to the CCN budget in a directly observable manner. Despite the near absence of NPF events in the boundary layer, Aitken mode particles were frequently measured, supporting the hypothesis of a free tropospheric source. Iodic acid and MSA were not found to participate in nucleation, however, MSA may contribute to aerosol growth via heterogeneous formation in the aqueous phase.
27 Nov 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 22. 10.1029/2021JD035126