Preprints
https://doi.org/10.5194/acp-2020-1054
https://doi.org/10.5194/acp-2020-1054

  27 Oct 2020

27 Oct 2020

Review status: a revised version of this preprint is currently under review for the journal ACP.

Coral reef-derived dimethyl sulfide and the climatic impact of the loss of coral reefs

Sonya L. Fiddes1,2,3,a, Matthew T. Woodhouse3, Todd P. Lane4, and Robyn Schofield4 Sonya L. Fiddes et al.
  • 1Australian-German Climate and Energy College, University of Melbourne, Parkville, Australia
  • 2ARC Centre of Excellence for Climate System Science, School of Earth Sciences, University of Melbourne, Parkville, Australia
  • 3Climate Science Centre, Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organisation, Aspendale, Australia
  • 4ARC Centre of Excellence for Climate Extremes, School of Earth Sciences, University of Melbourne, Parkville, Australia
  • anow at: the Australian Antarctic Program Partnership, Institute of Marine and Antarctic Science, University of Tasmania, Hobart, Australia

Abstract. Dimethyl sulfide (DMS) is a naturally occurring aerosol precursor gas which plays an important role in the global sulfur budget, aerosol formation and climate. While DMS is produced predominantly by phytoplankton, recent observational literature has suggested that corals and their symbionts produce a comparable amount of DMS, which is unaccounted for in models. It has further been hypothesised that the coral reef source of DMS may modulate regional climate. This hypothesis presents a particular concern given the current threat to coral reefs under anthropogenic climate change. In this paper, a global climate model with online chemistry and aerosol is used to explore the influence of coral reef-derived DMS on atmospheric composition and climate. A simple representation of coral reef-derived DMS is developed and added to a common DMS surface water climatology, resulting in an additional DMS flux of 0.3 Tg year−1 S, or 1.7 % of the global flux. By comparing the differences between both nudged and free running ensemble simulations with and without coral reef-derived DMS, the influence of coral reef-derived DMS on regional climate is quantified. In the Maritime Continent-Australian region, where the highest density of coral reefs exist, a small decrease in nucleation and Aitken mode aerosol number concentration and mass is found when coral reef DMS emissions are removed from the system. However, these small responses are found to have no robust effect on regional climate via direct and indirect aerosol effects. This work emphasises the complexities of the aerosol-climate system and the limitations of current modelling capabilities are highlighted, in particular surrounding convective responses to changes in aerosol. In conclusion we find no robust evidence that coral reef-derived DMS influences global and regional climate.

Sonya L. Fiddes et al.

 
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Sonya L. Fiddes et al.

Sonya L. Fiddes et al.

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Short summary
Coral reefs are known to produce the aerosol precursor dimethyl sulfide (DMS). Currently, this source of coral DMS is unaccounted for in climate modelling and the impact of coral reef extinction on aerosol and climate is unknown. In this study, we address this problem using a coupled chemistry-climate model for the first time. We find that coral reefs make a minimal contribution to the aerosol population, and are unlikely to play a role in climate modulation.
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