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Volume 17, issue 22 | Copyright

Special issue: Surface Ocean Aerosol Production (SOAP) (ACP/OS inter-journal...

Atmos. Chem. Phys., 17, 13645-13667, 2017
https://doi.org/10.5194/acp-17-13645-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Nov 2017

Research article | 16 Nov 2017

Overview and preliminary results of the Surface Ocean Aerosol Production (SOAP) campaign

Cliff S. Law1,2, Murray J. Smith1, Mike J. Harvey1, Thomas G. Bell3,4, Luke T. Cravigan5,6, Fiona C. Elliott1, Sarah J. Lawson7, Martine Lizotte8, Andrew Marriner1, John McGregor1, Zoran Ristovski6, Karl A. Safi9, Eric S. Saltzman4, Petri Vaattovaara10, and Carolyn F. Walker1 Cliff S. Law et al.
  • 1National Institute of Water and Atmospheric Research, Wellington, New Zealand
  • 2Department of Chemistry, University of Otago, Dunedin, New Zealand
  • 3Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, UK
  • 4Department of Earth System Science, University of California, Irvine, CA, USA
  • 5Climate Science Centre, Commonwealth Scientific and Industrial Research Organisation, Aspendale, Australia
  • 6International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Australia
  • 7Commonwealth Scientific and Industrial Research Organisation, Oceans and Atmosphere Flagship, Aspendale, Australia
  • 8Department of Biology (Québec-Océan), Université Laval, Québec City, Québec, Canada
  • 9National Institute of Water and Atmospheric Research, Hamilton, New Zealand
  • 10University of Eastern Finland, Kuopio, Finland

Abstract. Establishing the relationship between marine boundary layer (MBL) aerosols and surface water biogeochemistry is required to understand aerosol and cloud production processes over the remote ocean and represent them more accurately in earth system models and global climate projections. This was addressed by the SOAP (Surface Ocean Aerosol Production) campaign, which examined air–sea interaction over biologically productive frontal waters east of New Zealand. This overview details the objectives, regional context, sampling strategy and provisional findings of a pilot study, PreSOAP, in austral summer 2011 and the following SOAP voyage in late austral summer 2012. Both voyages characterized surface water and MBL composition in three phytoplankton blooms of differing species composition and biogeochemistry, with significant regional correlation observed between chlorophyll a and DMSsw. Surface seawater dimethylsulfide (DMSsw) and associated air–sea DMS flux showed spatial variation during the SOAP voyage, with maxima of 25nmolL−1 and 100µmolm−2d−1, respectively, recorded in a dinoflagellate bloom. Inclusion of SOAP data in a regional DMSsw compilation indicates that the current climatological mean is an underestimate for this region of the southwest Pacific. Estimation of the DMS gas transfer velocity (kDMS) by independent techniques of eddy covariance and gradient flux showed good agreement, although both exhibited periodic deviations from model estimates. Flux anomalies were related to surface warming and sea surface microlayer enrichment and also reflected the heterogeneous distribution of DMSsw and the associated flux footprint. Other aerosol precursors measured included the halides and various volatile organic carbon compounds, with first measurements of the short-lived gases glyoxal and methylglyoxal in pristine Southern Ocean marine air indicating an unidentified local source. The application of a real-time clean sector, contaminant markers and a common aerosol inlet facilitated multi-sensor measurement of uncontaminated air. Aerosol characterization identified variable Aitken mode and consistent submicron-sized accumulation and coarse modes. Submicron aerosol mass was dominated by secondary particles containing ammonium sulfate/bisulfate under light winds, with an increase in sea salt under higher wind speeds. MBL measurements and chamber experiments identified a significant organic component in primary and secondary aerosols. Comparison of SOAP aerosol number and size distributions reveals an underprediction in GLOMAP (GLObal Model of Aerosol Processes)-mode aerosol number in clean marine air masses, suggesting a missing marine aerosol source in the model. The SOAP data will be further examined for evidence of nucleation events and also to identify relationships between MBL composition and surface ocean biogeochemistry that may provide potential proxies for aerosol precursors and production.

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We carried out a multidisciplinary study to examine how aerosol production is influenced by the production and emission of trace gases and particles in the surface ocean. Phytoplankton blooms of different species composition in frontal waters southeast of New Zealand were a significant source of dimethylsulfide and other aerosol precursors. The relationships between surface ocean biogeochemistry and aerosol composition will inform the understanding of aerosol production over the remote ocean.
We carried out a multidisciplinary study to examine how aerosol production is influenced by the...
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