Preprints
https://doi.org/10.5194/acp-2021-680
https://doi.org/10.5194/acp-2021-680

  18 Aug 2021

18 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Full latitudinal marine atmospheric measurements of iodine monoxide

Hisahiro Takashima1,2, Yugo Kanaya2, Saki Kato1, Martina M. Friedrich3, Michel Van Roozendael3, Fumikazu Taketani2, Takuma Miyakawa2, Yuichi Komazaki2, Carlos A. Cuevas4, Alfonso Saiz-Lopez4, and Takashi Sekiya2 Hisahiro Takashima et al.
  • 1Faculty of Science, Fukuoka University, Fukuoka, Japan
  • 2Japan Agency for Marine–Earth Science and Technology (JAMSTEC), Yokohama, Japan
  • 3Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 4Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano (CSIC), Madrid, Spain

Abstract. Iodine compounds destroy ozone (O3) in the global troposphere and form new aerosols, thereby affecting the global radiative balance. However, few reports have described the latitudinal distribution of atmospheric iodine compounds. This work reports iodine monoxide (IO) measurements over unprecedented sampling areas from Arctic to the Southern Hemisphere and spanning sea surface temperatures (SSTs) of approximately 0 °C to 31.5 °C. The highest IO concentrations were observed over the Western Pacific warm pool (WPWP), where O3 minima were also measured. There, negative correlation was found between O3 and IO mixing ratios at extremely low O3 concentrations. This correlation is not explained readily by the “O3-dependent” oceanic fluxes of photolabile inorganic iodine compounds, the dominant source in recent global-scale chemistry-transport models representing iodine chemistry, and rather implies that “O3-independent” pathways can be similarly important in the WPWP. The O3-independent fluxes result in a 15 % greater O3 loss than that estimated for O3-dependent processes alone. The daily O3 loss rate related to iodine over the WPWP is as high as approximately 2 ppbv despite low O3 concentrations of ~10 ppbv, with the loss being up to 100 % greater than that without iodine. This finding suggests that warming SST driven by climate change may affect the marine atmospheric chemical balance through iodine–ozone chemistry.

Hisahiro Takashima et al.

Status: open (until 15 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-680', Anonymous Referee #1, 06 Sep 2021 reply

Hisahiro Takashima et al.

Hisahiro Takashima et al.

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Short summary
We have undertaken atmospheric iodine monoxide (IO) observations in the global marine boundary layer with a wide latitudinal coverage and sea surface temperature (SST) range. We conclude that atmospheric iodine is abundant over the Western Pacific warm pool, appearing as an “iodine fountain”, where ozone (O3) minima occur. Our study also found negative correlations between IO and O3 concentrations over IO maxima, which requires reconsideration of the initiation process of halogen activation.
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