Articles | Volume 17, issue 1
Atmos. Chem. Phys., 17, 385–402, 2017
Atmos. Chem. Phys., 17, 385–402, 2017
Research article
10 Jan 2017
Research article | 10 Jan 2017

Direct oceanic emissions unlikely to account for the missing source of atmospheric carbonyl sulfide

Sinikka T. Lennartz1, Christa A. Marandino1, Marc von Hobe2, Pau Cortes3, Birgit Quack1, Rafel Simo3, Dennis Booge1, Andrea Pozzer4, Tobias Steinhoff1, Damian L. Arevalo-Martinez1, Corinna Kloss2, Astrid Bracher5,6, Rüdiger Röttgers7, Elliot Atlas8, and Kirstin Krüger9 Sinikka T. Lennartz et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 2Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-7), Wilhelm-Johnen-Strasse, 52425 Jülich, Germany
  • 3Institut de Ciencies del Mar, CSIC, Pg. Maritim de la Barceloneta, 37-49, 08003 Barcelona, Catalonia, Spain
  • 4Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
  • 5Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bussestrasse 24, 27570 Bremerhaven, Germany
  • 6Institute of Environmental Physics, University of Bremen, 28334 Bremen, Germany
  • 7Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany
  • 8Rosenstiel School of Marine and Atmospheric Science, Miami, FL 33149, USA
  • 9University of Oslo, Department of Geosciences, 0315 Oslo, Norway

Abstract. The climate active trace-gas carbonyl sulfide (OCS) is the most abundant sulfur gas in the atmosphere. A missing source in its atmospheric budget is currently suggested, resulting from an upward revision of the vegetation sink. Tropical oceanic emissions have been proposed to close the resulting gap in the atmospheric budget. We present a bottom-up approach including (i) new observations of OCS in surface waters of the tropical Atlantic, Pacific and Indian oceans and (ii) a further improved global box model to show that direct OCS emissions are unlikely to account for the missing source. The box model suggests an undersaturation of the surface water with respect to OCS integrated over the entire tropical ocean area and, further, global annual direct emissions of OCS well below that suggested by top-down estimates. In addition, we discuss the potential of indirect emission from CS2 and dimethylsulfide (DMS) to account for the gap in the atmospheric budget. This bottom-up estimate of oceanic emissions has implications for using OCS as a proxy for global terrestrial CO2 uptake, which is currently impeded by the inadequate quantification of atmospheric OCS sources and sinks.

Short summary
We present new sea surface and marine boundary layer measurements of carbonyl sulfide, the most abundant sulfur gas in the atmosphere, and calculate an oceanic emission estimate. Our results imply that oceanic emissions are very unlikely to account for the missing source in the atmospheric budget that is currently discussed for OCS.
Final-revised paper