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.