Preprints
https://doi.org/10.5194/bg-2021-281
https://doi.org/10.5194/bg-2021-281

  12 Nov 2021

12 Nov 2021

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

Global modelling of soil carbonyl sulfide exchange

Camille Abadie1, Fabienne Maignan1, Marine Remaud1, Jérôme Ogée2, J. Elliott Campbell3, Mary E. Whelan4, Florian Kitz5, Felix M. Spielmann5, Georg Wohlfahrt5, Richard Wehr6, Wu Sun7, Nina Raoult1, Ulli Seibt8, Didier Hauglustaine1, Sinikka T. Lennartz9,10, Sauveur Belviso1, David Montagne11, and Philippe Peylin1 Camille Abadie et al.
  • 1Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
  • 2INRA, UMR 1391 ISPA, 33140 Villenave d’Ornon, France
  • 3Sierra Nevada Research Institute, University of California, Merced, California 95343, USA
  • 4Department of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA
  • 5Department of Ecology, University of Innsbruck, Innsbruck, 6020, Austria
  • 6Center for Atmospheric and Environmental Chemistry, Aerodyne Research, Inc., Billerica, Massachusetts, 01821, USA
  • 7Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305, USA
  • 8Department of Atmospheric & Oceanic Sciences, University of California Los Angeles, California 90095, USA
  • 9Institute of Chemistry and Biology of the Marine Environment, University of Oldenburg, 26129 Oldenburg, Germany
  • 10Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, 18 02139, MA, USA
  • 11AgroParisTech, INRAE, Université Paris-Saclay, UMR ECOSYS, 78850 Thiverval-Grignon, France

Abstract. Carbonyl sulfide (COS) is an atmospheric trace gas of interest for C cycle research because COS uptake by continental vegetation is strongly related to terrestrial gross primary productivity (GPP), the largest and most uncertain flux in atmospheric CO2 budgets. However, to use atmospheric COS budgets as an additional tracer of GPP, an accurate quantification of COS exchange by soils is also needed. At present, the atmospheric COS budget is unbalanced globally, with total COS flux estimates from oxic and anoxic soils that vary between −409 and −104 GgS yr−1. This uncertainty hampers the use of atmospheric COS concentrations to constrain GPP estimates through atmospheric transport inversions. In this study we implemented a mechanistic soil COS model in the ORCHIDEE land surface model to simulate COS fluxes in oxic and anoxic soils. Evaluation of the model against flux measurements at 7 sites yields a mean root mean square deviation of 1.6 pmol m−2 s−1, instead of 2 pmol m−2 s−1 when using a previous empirical approach that links soil COS uptake to soil heterotrophic respiration. The new model predicts that, globally and over the 2009–2016 period, oxic soils act as a net uptake of −126 GgS yr−1, and anoxic soils are a source of +96 GgS yr−1, leading to a global net soil sink of only −30 GgS yr−1, i.e., much smaller than previous estimates. The small magnitude of the soil fluxes suggests that the error in the COS budget is dominated by the much larger fluxes from plants, oceans, and industrial activities. The predicted spatial distribution of soil COS fluxes, with large emissions in the tropics from oxic (up to 68.2 pmol COS m−2 s−1) and anoxic (up to 36.8 pmol COS m−2 s−1) soils, marginally improves the latitudinal gradient of atmospheric COS concentrations, after transport by the LMDZ atmospheric transport model. The impact of different soil COS flux representations on the latitudinal gradient of the atmospheric COS concentrations is strongest in the northern hemisphere. We also implemented spatio-temporal variations of near-ground atmospheric COS concentrations in the modelling of biospheric COS fluxes, which helped reduce the imbalance of the atmospheric COS budget by lowering COS uptake by soils and vegetation globally (−10 % for soil, and −8 % for vegetation with a revised mean estimate of −576 GgS y−r1 over 2009–2016). Sensitivity analyses highlighted the different parameters to which each soil COS flux model is the most responsive, selected in a parameter optimization framework. Having both vegetation and soil COS fluxes modelled within ORCHIDEE opens the way for using observed ecosystem COS fluxes and larger scale atmospheric COS mixing ratios to improve the simulated GPP, through data assimilation techniques.

Camille Abadie et al.

Status: open (until 24 Dec 2021)

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Camille Abadie et al.

Camille Abadie et al.

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Short summary
A better constrain of the components of carbonyl sulfide (COS) global budget is needed to exploit its potential as a gross primary productivity proxy. In this study, we compare two representations of oxic soil COS fluxes, and we develop an approach to represent anoxic soil COS fluxes in a land surface model. We show the importance of atmospheric COS concentration variations on oxic soil COS fluxes and provide new estimates for oxic and anoxic soil contributions to the COS global budget.
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