Aerosol Production and Chemical Complexity

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Aerosol Production and Chemical Complexity

Process diagram of the various considerations involved in aerosol generation via bubble bursting.
[Collins et al., Atmos. Meas. Tech., 2014]

Most climate models currently represent aerosols produced at the ocean surface to be composed of entirely sea salt.  In addition, these models often assume that all of these particles are identical.  This simplistic view is clearly a poor representation of sea spray aerosol (SSA).  CAICE researchers are tackling our understanding of SSA production mechanisms and chemical composition using combined and integrated top-down and bottom-up approaches.

Several experimental and theoretical techniques are used to study the chemical complexity of nascent sea spray aerosol.  The amount of organic material that gets transferred from the ocean to the atmosphere can influence the reactive chemistry of these particles and their climate-relevant properties — each of these topics is a further focus of CAICE research.

Furthermore, in order to be able to predict what kinds of particles the ocean will emit, we must know how sea spray aerosol particles are produced at the ocean-atmosphere interface. The sea surface microlayer (SSML) resides at this interface and represents a rich, complex environmental system with its own chemical composition and biochemical activity.  The chemical composition, physical phase state, and internal structure of sea spray aerosol particles is related to the chemistry, physics, and biochemistry that occur at the ocean surface as well.  Researchers within CAICE are trying to understand the chemical processes that lead to differences in composition between bulk seawater, the SSML, and SSA.

We are learning that sea spray aerosol particles are much more than just small droplets of seawater.  In fact, the bubble bursting process that produces these small particles at the ocean surface leads to several interesting phenomena, including:

  • Sea spray aerosol particles are enriched in organic material compared to the seawater from which they were made.
  • The chemical composition of sea spray aerosol particles depends strongly on their size.  There are several different types of sea spray aerosol particles, including those that actually lack salt!