Marine and Terrestrial Organic Ice‐Nucleating Particles in Pristine Marine to Continentally Influenced Northeast Atlantic Air Masses

Abstract

Sea spray aerosol (SSA) generated by bubble bursting at the ocean surface is an important component of aerosol‐cloud interactions over remote oceans, providing the atmosphere with ice‐nucleating particles (INPs) or particles required for heterogeneous ice nucleation. Studies have shown that organic INPs are emitted during phytoplankton blooms, but changes in INP number concentrations (nINPs) due to ocean biological activity have not been directly demonstrated in natural SSA. In this study, a clean sector sampler was used to differentiate ice nucleation and composition of pristine SSA from terrestrial aerosol at the Mace Head Research Station in August 2015. Average nINPs active at −15 °C (nINPs,−15 °C) were 0.0011 L−1, and large variability (up to a factor of 200) was observed for INPs active warmer than −22 °C. Highest nINPs in the clean sector occurred during a period of elevated marine organic aerosol from offshore biological activity (M1, nINPs,−15 °C = 0.0077 L−1). A peak in nINPs was also observed in terrestrial organic aerosol (T1, nINPs,−15 °C = 0.0076 L−1). The impacts of heating and hydrogen peroxide digestion on nINPs indicate that INPs at Mace Head Research Station were largely organic and that INPs observed during M1 and T1 were biological (i.e., protein containing). Complexities of predicting increases in nINPs due to offshore biological activity are explored. A parameterization for pristine SSA INPs over the North Atlantic Ocean was developed, illustrating that SSA is associated with a factor of 1,000 fewer ice‐nucleating sites per surface area of aerosol compared to mineral dust.

Characteristics of Ice Nucleating Particles in and Around California Winter Storms

“…However, even a small number of these efficient ice nucleators can account for the majority of INPs (Cornwell, ). Measurements of INP surface site density ( n s ) was used to investigate the relative contribution of certain INP types by comparison to n s parameterizations for dust aerosol (Niemand et al, ; Ullrich et al, ) and clean marine INP (McCluskey, et al, ). During ACAPEX, n s values largely fell between these two bounding parameterizations, although with more values in the region of clean marine INPs.…”

“…Specifically, oceanic aerosol could be a potential source of INPs (McCluskey et al, ; McCluskey et al, ), especially since these storm systems travel for thousands of miles over the ocean and are associated with strong onshore flow leading to increased wave breaking. However, these marine INPs, while biogenic (McCluskey, Ovadnevaite , et al, ), are much less efficient ice nucleators than dust or terrestrially‐sourced biological (intended to mean microbial herein) particles (DeMott et al, ), and thus could lead to different cloud and precipitation properties if they were the dominant or only INP source. Another potential INP source is local soil particles (Hill et al, ) lofted by increased winds associated with the landfalling storm.…”

Observations of Ice Nucleating Particles Over Southern Ocean Waters

“…a) Ice nucleating particle (INP) temperature spectra from the Continuous Flow Diffusion Chamber (CFDC; crosses) and the ice spectrometer (IS) (circles) during CAPRICORN and from observations attributed to sea spray aerosol by DeMott et al (; gray shaded area). (b) Ice nucleation site densities ( n s ) for IS measurements during CAPRICORN (circles) and a parameterization for pristine North Atlantic air masses (dashed line; McCluskey, Ovadnevaite, et al, ). CAPRICORN = Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean.…”

“…Our understanding of the biological processes that control the production of INEs in seawater and the physicochemical processes that govern their release in SSA remains extremely limited. Applying marine INP parameterizations developed from specific ocean basins and seasons (McCluskey, Ovadnevaite et al, Wilson et al, ) to global marine INP emissions remains a necessary, but uncertain, assumption due to a lack of direct observations, particularly over the SO. In this study, INP observations made over the SO, south of Australia, will be used to (1) provide observational constraints for numerical predictions of n INPs and (2) investigate the composition of marine INPs in the SO region.…”

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

“…Until recently, the only systematic study of INPs in the marine boundary layer was that undertaken by Bigg [22]. Low INP levels over oceans and variable production of biological INPs has recently been documented in marine sea spray aerosol [18,23], and higher levels appear to be generated by planktonic blooms or the ensuing microbial succession [16,18,19,24,25]. Their emission from the ocean surface will likely be enhanced by their enrichment in the sea surface microlayer [17,26].…”