The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

The oceans represent a significant global source of atmospheric aerosols. Sea spray aerosol (SSA) particles comprise sea salts and organic species in varying proportions. In addition to size, the overall composition of SSA particles determines how effectively they can form cloud droplets and ice crystals. Thus, understanding the factors controlling SSA composition is critical to predicting aerosol impacts on clouds and climate. It is often assumed that submicrometer SSAs are mainly formed by film drops produced from bursting bubble-cap films, which become enriched with hydrophobic organic species contained within the sea surface microlayer. In contrast, jet drops formed from the base of bursting bubbles are postulated to mainly produce larger supermicrometer particles from bulk seawater, which comprises largely salts and water-soluble organic species. However, here we demonstrate that jet drops produce up to 43% of total submicrometer SSA number concentrations, and that the fraction of SSA produced by jet drops can be modulated by marine biological activity. We show that the chemical composition, organic volume fraction, and ice nucleating ability of submicrometer particles from jet drops differ from those formed from film drops. Thus, the chemical composition of a substantial fraction of submicrometer particles will not be controlled by the composition of the sea surface microlayer, a major assumption in previous studies. This finding has significant ramifications for understanding the factors controlling the mixing state of submicrometer SSA particles and must be taken into consideration when predicting SSA impacts on clouds and climate.

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Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-13903-2021 ◽

2021 ◽

Vol 21 (18) ◽

pp. 13903-13930

Author(s):

Robert Wagner ◽

Luisa Ickes ◽

Allan K. Bertram ◽

Nora Els ◽

Elena Gorokhova ◽

...

Keyword(s):

Aerosol Particles ◽

Ice Nucleation ◽

Sea Surface ◽

Ice Formation ◽

Sea Spray ◽

Surface Microlayer ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

Seawater Samples ◽

Heterogeneous Ice Nucleation

Abstract. Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea spray aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 K are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (Skeletonema marinoi). The particles were suspended in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 K, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about 5×1010 m−2 at an ice saturation ratio of 1.3. Much smaller densities in the range of 108–109 m−2 were observed at temperatures between 220 and 235 K, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are 2 orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the number of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how instrumental parameters like the aerosolisation method and the ice nucleation measurement technique might affect the comparability of the results amongst different studies.

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Calcium bridging drives polysaccharide co-adsorption to a proxy sea surface microlayer

Physical Chemistry Chemical Physics ◽

10.1039/d1cp01407b ◽

2021 ◽

Author(s):

Kimberly Anne Carter-Fenk ◽

Abigal Dommer ◽

Michelle E. Fiamingo ◽

Jeongin Kim ◽

Rommie Amaro ◽

...

Keyword(s):

Organic Carbon ◽

Mass Fraction ◽

Co Adsorption ◽

Ocean Surface ◽

Sea Surface ◽

Sea Spray ◽

Surface Microlayer ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

Significant Mass

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Influence of sea surface microlayers and phytoplankton blooms on sea spray aerosol hygroscopicity and the possible implications for mixed-phase clouds

10.5194/egusphere-egu21-9765 ◽

2021 ◽

Author(s):

Sigurd Christiansen ◽

Luisa Ickes ◽

Ines Bulatovic ◽

Caroline Leck ◽

Benjamin Murray ◽

...

Keyword(s):

Chemical Composition ◽

Mixed Phase ◽

Sea Surface ◽

Sea Spray ◽

Surface Microlayer ◽

Cloud Properties ◽

Aerosol Emission ◽

Sea Spray Aerosol ◽

Mixed Phase Clouds ◽

Aerosol Hygroscopicity

Introduction: Breaking waves on the ocean surface lead to sea spray aerosol emission to the atmosphere. Sea spray aerosols are a major source of uncertainty in climate models. The physical processes governing sea spray aerosol production play an important part in determining sea spray aerosol emission, size distribution, and chemical composition. Sea spray often contains organic material, but it is unclear how this material affects the ability of particles to act as cloud condensation nuclei (CCN).Methods: We have measured the CCN-derived hygroscopicity of different types of aerosol particles generated from the following seawater proxies and real seawater using a sea spray simulation tank (Christiansen et al., 2019), AEGOR, or an atomizer in a laboratory setup (Christiansen et al., 2020):&#160;<ul><li>Artificial seawater</li> <li>Artificial seawater spiked with diatoms cultured in the laboratory</li> <li>Samples of sea surface microlayer (SML) collected during field campaigns in the North Atlantic and Arctic Ocean.</li> <li>A continuous supply of fresh seawater during a three-week field campaign (June 2019) on the Faroe Islands, while following oceanic biogeochemical parameters.&#160; &#160;</li> </ul>Large-eddy simulation (LES) has been used to evaluate the general role of aerosol hygroscopicity in governing mixed-phase low-level cloud properties in the high Arctic.Conclusions:&#160; <ul><li>We show that sea spray aerosols generated using diatom cultures and surface microlayer water exhibit CCN activity similar to that of inorganic sea salt (&#954; value of &#8764;1.0), independent of dry particle size (50, 75, and 100 nm).</li> <li>The critical supersaturation of dry 80 nm SSA was relatively invariable (0.158&#177;0.04%), corresponding to the overall hygroscopicity parameter &#954; of 1.08&#177;0.05% derived from CCN during the phytoplankton bloom. This is despite indications that the chemical composition of both the seawater and the SSA were impacted by the presence of the phytoplankton.</li> <li>For accumulation mode aerosol, the simulated mixed-phase cloud properties do not depend strongly on &#954;, unless &#954; < 0.4. In addition, the cloud is sustained for all simulated cases.</li> <li>For Aitken mode aerosol, the hygroscopicity is more important changing the microphysical structure of the cloud and its radiative properties; here the particles can sustain the cloud only when &#954; &#8805; 0.4.&#160;</li> </ul>The experimental and model results combined suggest that the internal mixing of biogenic organic components in SSA does not have a substantial impact on the cloud droplet activation process and the cloud lifetime in Arctic mixed-phase clouds.References: Christiansen et al. (2020). J. Geophys. Res. Atm. https://doi.org/10.1029/2020JD032808 Christiansen et al. (2019). Environ. Sci. Technol. https://doi.org/10.1021/acs.est.9b04078&#160;

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Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

10.5194/acp-2021-252 ◽

2021 ◽

Author(s):

Robert Wagner ◽

Luisa Ickes ◽

Allan K. Bertram ◽

Nora Els ◽

Elena Gorokhova ◽

...

Keyword(s):

Aerosol Particles ◽

Ice Nucleation ◽

Sea Surface ◽

Ice Formation ◽

Sea Spray ◽

Surface Microlayer ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

Seawater Samples ◽

Heterogeneous Ice Nucleation

Abstract. Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea salt aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 K are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (Skeletonema marinoi). The particles were suspended in a large cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 K, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about 5·1010 m−2 at an ice saturation ratio of 1.3. Much smaller densities in the range of 108–109 m−2 were observed at temperatures between 220 and 235 K, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are two orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the amount of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how far instrumental parameters like the aerosolisation method and the ice-nucleation measurement technique might affect the comparability of the results amongst different studies.

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Water-Soluble Organic Composition of the Arctic Sea Surface Microlayer and Association with Ice Nucleation Ability

Environmental Science & Technology ◽

10.1021/acs.est.7b04072 ◽

2018 ◽

Vol 52 (4) ◽

pp. 1817-1826 ◽

Cited By ~ 9

Author(s):

Rosie J. Chance ◽

Jacqueline F. Hamilton ◽

Lucy J. Carpenter ◽

Sina C. Hackenberg ◽

Stephen J. Andrews ◽

...

Keyword(s):

Ice Nucleation ◽

Water Soluble ◽

Sea Surface ◽

The Arctic ◽

Surface Microlayer ◽

Organic Composition ◽

Sea Surface Microlayer ◽

Arctic Sea

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The ice-nucleating activity of Arctic sea surface microlayer samples and marine algal cultures

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11089-2020 ◽

2020 ◽

Vol 20 (18) ◽

pp. 11089-11117 ◽

Cited By ~ 3

Author(s):

Luisa Ickes ◽

Grace C. E. Porter ◽

Robert Wagner ◽

Michael P. Adams ◽

Sascha Bierbauer ◽

...

Keyword(s):

Ice Nucleation ◽

Sea Surface ◽

The Arctic ◽

Sea Spray ◽

Surface Microlayer ◽

Phytoplankton Species ◽

Sea Surface Microlayer ◽

Nucleation Activity ◽

Ice Nucleation Activity ◽

Algal Cultures

Abstract. In recent years, sea spray as well as the biological material it contains has received increased attention as a source of ice-nucleating particles (INPs). Such INPs may play a role in remote marine regions, where other sources of INPs are scarce or absent. In the Arctic, these INPs can influence water–ice partitioning in low-level clouds and thereby the cloud lifetime, with consequences for the surface energy budget, sea ice formation and melt, and climate. Marine aerosol is of a diverse nature, so identifying sources of INPs is challenging. One fraction of marine bioaerosol (phytoplankton and their exudates) has been a particular focus of marine INP research. In our study we attempt to address three main questions. Firstly, we compare the ice-nucleating ability of two common phytoplankton species with Arctic seawater microlayer samples using the same instrumentation to see if these phytoplankton species produce ice-nucleating material with sufficient activity to account for the ice nucleation observed in Arctic microlayer samples. We present the first measurements of the ice-nucleating ability of two predominant phytoplankton species: Melosira arctica, a common Arctic diatom species, and Skeletonema marinoi, a ubiquitous diatom species across oceans worldwide. To determine the potential effect of nutrient conditions and characteristics of the algal culture, such as the amount of organic carbon associated with algal cells, on the ice nucleation activity, Skeletonema marinoi was grown under different nutrient regimes. From comparison of the ice nucleation data of the algal cultures to those obtained from a range of sea surface microlayer (SML) samples obtained during three different field expeditions to the Arctic (ACCACIA, NETCARE, and ASCOS), we found that they were not as ice active as the investigated microlayer samples, although these diatoms do produce ice-nucleating material. Secondly, to improve our understanding of local Arctic marine sources as atmospheric INPs we applied two aerosolization techniques to analyse the ice-nucleating ability of aerosolized microlayer and algal samples. The aerosols were generated either by direct nebulization of the undiluted bulk solutions or by the addition of the samples to a sea spray simulation chamber filled with artificial seawater. The latter method generates aerosol particles using a plunging jet to mimic the process of oceanic wave breaking. We observed that the aerosols produced using this approach can be ice active, indicating that the ice-nucleating material in seawater can indeed transfer to the aerosol phase. Thirdly, we attempted to measure ice nucleation activity across the entire temperature range relevant for mixed-phase clouds using a suite of ice nucleation measurement techniques – an expansion cloud chamber, a continuous-flow diffusion chamber, and a cold stage. In order to compare the measurements made using the different instruments, we have normalized the data in relation to the mass of salt present in the nascent sea spray aerosol. At temperatures above 248 K some of the SML samples were very effective at nucleating ice, but there was substantial variability between the different samples. In contrast, there was much less variability between samples below 248 K. We discuss our results in the context of aerosol–cloud interactions in the Arctic with a focus on furthering our understanding of which INP types may be important in the Arctic atmosphere.

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Calcium Bridging Drives Polysaccharide Co-Adsorption to a Proxy Sea Surface Microlayer

10.26434/chemrxiv.14347265 ◽

2021 ◽

Author(s):

Kimberly Carter-Fenk ◽

Abigail Dommer ◽

Michelle E Fiamingo ◽

Jeongin Kim ◽

Rommie Amaro ◽

...

Keyword(s):

Palmitic Acid ◽

Surface Coverage ◽

Co Adsorption ◽

Sea Surface ◽

Interfacial Region ◽

Surface Microlayer ◽

Insoluble Organic Matter ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

Dynamics Simulations

Saccharides comprise a significant mass fraction of organic carbon in sea spray aerosol (SSA), but the mechanisms through which saccharides are transferred from seawater to the ocean surface and eventually into SSA are unclear. It is hypothesized that saccharides cooperatively adsorb to other insoluble organic matter at the air/sea interface, known as the sea surface microlayer (SSML). Using a combination of surface-sensitive infrared reflection-absorption spectroscopy and all-atom molecular dynamics simulations, we demonstrate that the marine-relevant, anionic polysaccharide alginate co-adsorbs to an insoluble palmitic acid monolayer via divalent cationic bridging interactions. Ca2+ induces the greatest extent of alginate co-adsorption to the monolayer, evidenced by the ~30% increase in surface coverage, whereas Mg2+ only facilitates one-third the extent of co-adsorption at seawater-relevant cation concentrations due to its strong hydration propensity. Na+ cations alone do not facilitate alginate co-adsorption, and palmitic acid protonation hinders the formation of divalent cationic bridges between the palmitate and alginate carboxylate moieties. Alginate co-adsorption is largely confined to the interfacial region beneath the monolayer headgroups, so surface pressure, and thus monolayer surface coverage, only changes the amount of alginate co-adsorption by less than 5%. Our results provide physical and molecular characterization of a potentially significant polysaccharide enrichment mechanism within the SSML.

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The Impact of Divalent Cations on the Enrichment of Soluble Saccharides in Primary Sea Spray Aerosol

Atmosphere ◽

10.3390/atmos9120476 ◽

2018 ◽

Vol 9 (12) ◽

pp. 476 ◽

Cited By ~ 6

Author(s):

Steven Schill ◽

Susannah Burrows ◽

Elias Hasenecz ◽

Elizabeth Stone ◽

Timothy Bertram

Keyword(s):

Divalent Cation ◽

Organic Material ◽

Large Fraction ◽

Co Adsorption ◽

Sea Spray ◽

Surface Microlayer ◽

Volume Fractions ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

The Impact

Field measurements have shown that sub-micrometer sea spray aerosol (SSA) is significantly enriched in organic material, of which a large fraction has been attributed to soluble saccharides. Existing mechanistic models of SSA production struggle to replicate the observed enhancement of soluble organic material. Here, we assess the role for divalent cation mediated co-adsorption of charged surfactants and saccharides in the enrichment of soluble organic material in SSA. Using measurements of particle supersaturated hygroscopicity, we calculate organic volume fractions for molecular mimics of SSA generated from a Marine Aerosol Reference Tank. Large enhancements in SSA organic volume fractions (Xorg > 0.2) were observed for 50 nm dry diameter (dp) particles in experiments where cooperative ionic interactions were favorable (e.g., palmitic acid, Mg2+, and glucuronic acid) at seawater total organic carbon concentrations (<1.15 mM C) and ocean pH. Significantly smaller SSA organic volume fractions (Xorg < 1.5 × 10−3) were derived from direct measurements of soluble saccharide concentrations in collected SSA with dry diameters <250 nm, suggesting that organic enrichment is strongly size dependent. The results presented here indicate that divalent cation mediated co-adsorption of soluble organics to insoluble surfactants at the ocean surface may contribute to the enrichment of soluble saccharides in SSA. The extent to which this mechanism explains the observed enhancement of saccharides in nascent SSA depends strongly on the concentration, speciation, and charge of surfactants and saccharides in the sea surface microlayer.

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A numerical framework for simulating episodic emissions of high-temperature marine INPs

10.5194/acp-2021-316 ◽

2021 ◽

Author(s):

Isabelle Steinke ◽

Paul J. DeMott ◽

Grant Deane ◽

Thomas C. J. Hill ◽

Mathew Maltrud ◽

...

Keyword(s):

Boundary Layer ◽

High Temperature ◽

Atmospheric Boundary Layer ◽

Heterotrophic Bacteria ◽

Sea Spray ◽

Surface Microlayer ◽

Partial Explanation ◽

Sea Surface Microlayer ◽

Sea Spray Aerosol ◽

Field Campaigns

Abstract. We present a framework for estimating concentrations of episodically elevated high-temperature marine ice nucleating particles (INPs) in the sea surface microlayer and their subsequent emission into the atmospheric boundary layer. These episodic INPs have been observed in multiple ship-based and coastal field campaigns, but the processes controlling their ocean concentrations and transfer to the atmosphere are not yet fully understood. We use a combination of empirical constraints and simulation outputs from an Earth System Model to explore different hypotheses for explaining the variability of INP concentrations, and the occurrence of episodic INPs, in the marine atmosphere. In our calculations, we examine two proposed oceanic sources of high-temperature INPs: heterotrophic bacteria and marine biopolymer aggregates (MBPAs). Furthermore, we assume that the emission of these INPs is determined by the production of supermicron sea spray aerosol formed from jet drops, with an entrainment probability that is described by Poisson statistics. The concentration of jet drops is derived from the number concentration of supermicron sea spray aerosol calculated from model runs. We then derive the resulting number concentrations of marine high-temperature INPs (≥ 253 K) in the atmospheric boundary layer and compare their variability to atmospheric observations of INP variability. Specifically, we compare against concentrations of episodically occurring high-temperature INPs observed during field campaigns in the Southern Ocean, the Equatorial Pacific, and the North Atlantic. We find that heterotrophic bacteria and MBPAs acting as INPs provide only a partial explanation for the observed high INP concentrations. We note, however, that there are still substantial knowledge gaps, particularly concerning the identity of the oceanic INPs contributing most frequently to episodic high-temperature INPs, their specific ice nucleation activity, and the enrichment of their concentrations during the sea-air transfer process. Therefore, targeted measurements investigating the composition of these marine INPs as well as drivers for their emission are needed, ideally in combination with modeling studies focused on the potential cloud impacts of these high-temperature INPs.

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