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The effect of seawater salinity on sea spray aerosol production
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  • Julika Zinke,
  • E. Douglas Nilsson,
  • Paul Zieger,
  • Matthew Edward Salter
Julika Zinke
Stockholm University

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E. Douglas Nilsson
Stockholm University
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Paul Zieger
Stockholm University
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Matthew Edward Salter
Stockholm University
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Abstract

To improve our understanding of the impact of sea spray aerosols (SSA) on the Earth’s climate, it is critical to understand the physical mechanisms which determine the size-resolved sea spray aerosol source. Of the factors affecting SSA emissions, seawater salinity has perhaps received the least attention in the literature and previous studies have produced conflicting results. Here, we present a series of laboratory experiments designed to investigate the role of salinity on aerosol production from artificial seawater using a continuous plunging jet. During these experiments, the aerosol and surface bubble size distributions were monitored while the salinity was decreased from 35 to 0 g/kg. Three distinct salinity regimes were identified: 1) A high salinity regime, 10-35 g/kg, where decreasing salinity only resulted in minor reductions in particle number emissions but significant reductions in particle volume; 2) an intermediate salinity regime, 5-10 g/kg, with a local maximum in particle number; 3) a low salinity regime, < 5 g/kg, characterized by a rapid decrease in particle number as salinity decreased and dominated by small particles and larger bubbles. We discuss the implications of our results through comparison of the size-resolved aerosol flux and the surface bubble population at different salinities. Finally, by varying the seawater temperature at three specific salinities we have also generated a simple parameterization of the particle number concentration and effective radius as a function of seawater temperature and salinity that can be used to estimate the sea spray aerosol flux in low salinity regions like the Baltic Sea.