A Dynamic Link between Ice Nucleating Particles Released in Nascent Sea Spray Aerosol and Oceanic Biological Activity during Two Mesocosm Experiments

Abstract

Emission rates and properties of ice nucleating particles (INPs) are required for proper representation of aerosol–cloud interactions in atmospheric models. Few investigations have quantified marine INP emissions, a potentially important INP source for remote oceanic regions. Previous studies have suggested INPs in sea spray aerosol (SSA) are linked to oceanic biological activity. This proposed link was explored in this study by measuring INP emissions from nascent SSA during phytoplankton blooms during two mesocosm experiments. In a Marine Aerosol Reference Tank (MART) experiment, a phytoplankton bloom was produced with chlorophyll-a (Chl a) concentrations reaching 39 μg L−1, while Chl a concentrations more representative of natural ocean conditions were obtained during the Investigation into Marine Particle Chemistry and Transfer Science (IMPACTS; peak Chl a of 5 μg L−1) campaign, conducted in the University of California, San Diego, wave flume. Dynamic trends in INP emissions occurred for INPs active at temperatures > −30°C. Increases in INPs active between −25° and −15°C lagged the peak in Chl a in both studies, suggesting a consistent population of INPs associated with the collapse of phytoplankton blooms. Trends in INP emissions were also compared to aerosol composition, abundances of microbes, and enzyme activity. In general, increases in INP concentrations corresponded to increases in organic species in SSA and the emissions of heterotrophic bacteria, suggesting that both microbes and biomolecules contribute to marine INP populations. INP trends were not directly correlated with a single biological marker in either study. Direct measurements of INP chemistry are needed to accurately identify particles types contributing to marine INP populations.

Biological Impacts on Carbon Speciation and Morphology of Sea Spray Aerosol

“…Determining the mass fraction of CO 3 2− with respect to total carbon is challenging without the availability of appropriate standards for the organic component. While it is possible for radiation damage to cause the appearance of C*O 3 in STXM chambers open to the air, 41 this was not observed during the course of these experiments; spectra for standard compounds showed no resolvable contribution from the C*O 3 transition. Furthermore, the STXM chamber used here was evacuated and backfilled with helium to avoid unwanted reaction of gases with particles in these studies.…”

Abundance of Biological Ice Nucleating Particles in the Mississippi and Its Major Tributaries

“…In addition to ongoing interest into the action of both mineral dusts and soot [6][7][8], the role of the soil organic matter, which includes INPs produced by the decomposer community, as a source of atmospheric INPs is now being more closely examined [9][10][11][12]; pioneering work identified the litter layer, in particular, as a prodigious source of biological INPs in diverse global ecotypes [13,14]. By contrast, while oceans comprise 71% of the Earth's surface area and emit INPs within sea spray-mainly by bubble bursting-they are only now being investigated more systematically [15][16][17][18][19][20][21]. Until recently, the only systematic study of INPs in the marine boundary layer was that undertaken by Bigg [22].…”

Global relevance of marine organic aerosols as ice nucleating particles

“…This value lies in the lower end of the range of factors recommended by Turpin and Lim (2001) for non-urban cites, and is chosen since we are only considering water insoluble organics, which are associated with lower carbon-to-molecule conversion in their study. Subsequent publications which investigated air borne sea spray aerosols produced in laboratory settings (DeMott et al, 2016;McCluskey et al, 2017) have, however, indicated much lower ice nucle-15 ation efficiencies than that described by Wilson et al (2015). Therefore a sensitivity study is also performed by producing a fit to data published in DeMott et al (2016).…”

“…Suggested INP candidates, such as mineral dust, terrestrial biogenic material, and black carbon, are mostly of terrestrial origin. Recently, however, more interest has been drawn to oceans being possible sources of ice-5 active organic matter (Bigg, 1973;Knopf et al, 2011;Wang et al, 2015;Wilson et al, 2015;DeMott et al, 2016;McCluskey et al, 2017). While likely not as effective an INP as mineral dust, the difference in geographical locations of their emission sources may cause such marine organic aerosols (MOA) to become an important source of INPs in remote marine regions.…”