Preprints
https://doi.org/10.5194/bg-2020-463
https://doi.org/10.5194/bg-2020-463

  08 Jan 2021

08 Jan 2021

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

Evaluation of ocean dimethylsulfide concentration and emission in CMIP6 models

Josué Bock1, Martine Michou1, Pierre Nabat1, Manabu Abe2, Jane P. Mulcahy3, Dirk J. L. Olivié4, Jörg Schwinger5, Parvadha Suntharalingam6, Jerry Tjiputra5, Marco van Hulten7, Michio Watanabe2, Andrew Yool8, and Roland Séférian1 Josué Bock et al.
  • 1CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, France
  • 2Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
  • 3Met Office Hadley Center, Exeter, UK
  • 4Norwegian Meteorological Institute, Oslo, Norway
  • 5NORCE Climate and Bjerknes Centre for Climate Research, Bergen, Norway
  • 6School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
  • 7Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • 8National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom

Abstract. Characteristics and trends of surface ocean dimethylsulfide (DMS) concentrations and fluxes into the atmosphere of four Earth System Models (ESMs: CNRM-ESM2-1, MIROC-ES2L, NorESM2-LM and UKESM1-0-LL) are analysed over the recent past (1980–2009) and into the future, using Coupled Model Intercomparison Project 6 (CMIP6) simulations. The DMS concentrations in historical simulations systematically underestimate the most widely-used observed climatology, but compare more favourably against two recent observation based datasets. The models better reproduce observations in mid to high latitudes, as well as in polar and westerlies marine biomes. The resulting multi-model estimate of contemporary global ocean DMS emissions is of 16–24 Tg S year−1, which is narrower than the observational-derived range of 16 to 28 Tg S year−1. The four models disagree on the sign of the trend of the global DMS flux from 1980 onwards, with two models showing an increase and two models a decrease. At the global scale, these trends are dominated by changes in surface DMS concentrations in all models, irrespective of the air-sea flux parameterisation used. In turn, three models consistently show that changes in DMS concentrations are correlated with changes in marine productivity, however the latter is poorly constrained in the current generation of ESMs, thus limiting the predictive ability of this relationship. In contrast, a consensus is found among all models over polar latitudes where an increasing trend is predominantly driven by the retreating sea-ice extent. However, the magnitude of this trend between models differs by a factor of three, from 2.9 to 9.2 Gg S decade−1 over the period 1980–2014, which is at the low end of a recent satellite-derived analysis. Similar increasing trends are found in climate projections over the 21st century.

Josué Bock 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 bg-2020-463', Martí Galí, 29 Jan 2021
  • RC2: 'Comment on bg-2020-463', Anonymous Referee #2, 24 Feb 2021
  • RC3: 'Comment on bg-2020-463', Nadja Steiner, 25 Feb 2021

Josué Bock et al.

Josué Bock et al.

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Short summary
In this study we analyse surface ocean dimethylsulfide (DMS) concentration and flux to the atmosphere from four CMIP6 Earth System Models over the historical and ssp585 simulations. Our analysis of contemporary (1980–2009) climatologies shows that models better reproduce observations in mid to high latitudes. The models disagree on the sign of the trend of the global DMS flux from 1980 onwards. The models agree on a positive trend of DMS over polar latitudes following sea-ice retreat dynamics.
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