Organic aerosols, a ubiquitous component of atmospheric particulate matter,
are still poorly constrained in global models. New sources and production
mechanisms have been discovered in the last few years, including primary and
secondary sources from the ocean, important new terrestrial secondary
organic aerosol precursors, and cloud processing. Although their importance
for gas-phase chemistry and climate is expected to be very significant, most
global models to date include few, if any, of these new sources.

Marine primary aerosols are traditionally being treated in global models as
pure sea-salt. Recently, however, it has been well established that
sea-spray composition consists of a mixture of sea-salt and water insoluble
organic material. This is expected to affect marine aerosol properties in
global models, with probably the most notable change being that the mixed
particles have reduced hygroscopicity. This results in an increase of marine
aerosol lifetime due to suppressed removal, as well as a reduction of their
cloud condensation nuclei activity, affecting cloud droplet number
concentration, and, consequently, altering the radiation that reaches the
ground, feeding back to affect ocean biology, which is the source of
organics in sea-spray.

The importance of the oceanic source of primary organic aerosols will be
evaluated and validated against measurements, in conjunction with sea-salt.
The calculated changes in both sea-salt and organic aerosol distribution due
to the new marine organic aerosol source will be evaluated. The importance
of the marine organic aerosols on both direct and indirect effects and the
potential feedbacks involved will be presented.

Authors: Kostas Tsigaridis, Dorothy Koch and Surabi Menon