Marine iodine emissions in a changing world

Lucy J. Carpenter*, Rosie J. Chance, Tomás Sherwen, Thomas J. Adams, Stephen M. Ball, Mat J. Evans, Helmke Hepach, Lloyd D.J. Hollis, Claire Hughes, Timothy D. Jickells, Anoop Mahajan, David P. Stevens, Liselotte Tinel, Martin R. Wadley

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


Iodine is a critical trace element involved in many diverse and important processes in the Earth system. The importance of iodine for human health has been known for over a century, with low iodine in the diet being linked to goitre, cretinism and neonatal death. Research over the last few decades has shown that iodine has significant impacts on tropospheric photochemistry, ultimately impacting climate by reducing the radiative forcing of ozone (O 3) and air quality by reducing extreme O 3 concentrations in polluted regions. Iodine is naturally present in the ocean, predominantly as aqueous iodide and iodate. The rapid reaction of sea-surface iodide with O 3 is believed to be the largest single source of gaseous iodine to the atmosphere. Due to increased anthropogenic O 3, this release of iodine is believed to have increased dramatically over the twentieth century, by as much as a factor of 3. Uncertainties in the marine iodine distribution and global cycle are, however, major constraints in the effective prediction of how the emissions of iodine and its biogeochemical cycle may change in the future or have changed in the past. Here, we present a synthesis of recent results by our team and others which bring a fresh perspective to understanding the global iodine biogeochemical cycle. In particular, we suggest that future climate-induced oceanographic changes could result in a significant change in aqueous iodide concentrations in the surface ocean, with implications for atmospheric air quality and climate.

Original languageEnglish
Article number20200824
Number of pages17
JournalProceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number2247
Early online date3 Mar 2021
Publication statusPublished - 31 Mar 2021

Bibliographical note

Funding Information:
Data accessibility. The compiled seawater iodide data from this study are publicly available at BODC (https:// and described in Chance et al. [50]. Authors’ contributions. L.J.C. and R.J.C. conceived of the study; L.J.C. coordinated the study and drafted the manuscript; H.H., C.H. and R.J.C. designed and carried out the incubation studies; M.R.W., D.P.S. and T.D.J. participated in the design of the ocean iodine modelling and M.R.W. carried it out; T.S. and M.J.E. designed the atmospheric modelling and T.S. carried it out; T.J.A., L.D.J.H., L.T. and S.M.B. carried out I2 emission experiments; T.S. and R.J.C. synthesized global iodide data; A.M. coordinated cruise participation; T.D.J., R.J.C., M.R.W., A.M. and T.S. critically revised the manuscript. Competing interests. The authors declare no competing interests. Funding. This work was funded by the Natural Environment Research Council (NERC), UK, through the grant ‘Iodide in the ocean: distribution and impact on iodine flux and ozone loss’ (NE/N009983/1 University of York, NE/N01054X/1 University of East Anglia and NE/N009444/1 University of Leicester). L.J.C. also acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 program (Grant agreement no. 833290). Acknowledgements. Model runs for this work were undertaken on the Viking Cluster, which is a high-performance computer facility provided by the University of York. We are grateful for computational support from the University of York High Performance Computing service, Viking and the Research Computing team. For the ocean model runs we acknowledge the support of resources provided by the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia.

Publisher Copyright:
© 2021 The Authors.

Copyright 2021 Elsevier B.V., All rights reserved.


  • global iodine cycle
  • halogens
  • iodide
  • iodine
  • ozone
  • sea-air interactions

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