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1. Acidity across the interface from the ocean surface to sea spray aerosol

   https://doi.org/10.1073/pnas.2018397118  

   Angle, Kyle J.; Crocker, Daniel R.; Simpson, Rebecca M.; Mayer, Kathryn J.; Garofalo, Lauren A.; Moore, Alexia N.; Mora Garcia, Stephanie L.; Or, Victor W.; Srinivasan, Sudarshan; Farhan, Mahum; et al (December 2020, Proceedings of the National Academy of Sciences)

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   Aerosols impact climate, human health, and the chemistry of the atmosphere, and aerosol pH plays a major role in the physicochemical properties of the aerosol. However, there remains uncertainty as to whether aerosols are acidic, neutral, or basic. In this research, we show that the pH of freshly emitted (nascent) sea spray aerosols is significantly lower than that of sea water (approximately four pH units, with pH being a log scale value) and that smaller aerosol particles below 1 μm in diameter have pH values that are even lower. These measurements of nascent sea spray aerosol pH, performed in a unique ocean−atmosphere facility, provide convincing data to show that acidification occurs “across the interface” within minutes, when aerosols formed from ocean surface waters become airborne. We also show there is a correlation between aerosol acidity and dissolved carbon dioxide but no correlation with marine biology within the seawater. We discuss the mechanisms and contributing factors to this acidity and its implications on atmospheric chemistry. 

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2. Atmospheric particle abundance and sea salt aerosol observations in the springtime Arctic: a focus on blowing snow and leads

   https://doi.org/10.5194/acp-22-15263-2022  

   Chen, Qianjie; Mirrielees, Jessica A.; Thanekar, Sham; Loeb, Nicole A.; Kirpes, Rachel M.; Upchurch, Lucia M.; Barget, Anna J.; Lata, Nurun Nahar; Raso, Angela R.; McNamara, Stephen M.; et al (January 2022, Atmospheric Chemistry and Physics)

   Abstract. Sea salt aerosols play an important role in the radiationbudget and atmospheric composition over the Arctic, where the climate israpidly changing. Previous observational studies have shown that Arctic sea ice leads are an important source of sea salt aerosols, and modeling efforts have also proposed blowing snow sublimation as a source. In this study,size-resolved atmospheric particle number concentrations and chemicalcomposition were measured at the Arctic coastal tundra site ofUtqiaġvik, Alaska, during spring (3 April–7 May 2016). Blowing snow conditions were observed during 25 % of the 5-week study period andwere overpredicted by a commonly used blowing snow parameterization based solely on wind speed and temperature. Throughout the study, open leads werepresent locally. During periods when blowing snow was observed, significantincreases in the number concentrations of 0.01–0.06 µm particles(factor of 6, on average) and 0.06–0.3 µm particles (67 %, on average) and a significant decrease (82 %, on average) in 1–4 µmparticles were observed compared to low wind speed periods. These size distribution changes were likely caused by the generation of ultrafineparticles from leads and/or blowing snow, with scavenging of supermicronparticles by blowing snow. At elevated wind speeds, both submicron andsupermicron sodium and chloride mass concentrations were enhanced,consistent with wind-dependent local sea salt aerosol production. Atmoderate wind speeds below the threshold for blowing snow as well as during observed blowing snow, individual sea spray aerosol particles were measured.These individual salt particles were enriched in calcium relative to sodiumin seawater due to the binding of this divalent cation with organic matter in the sea surface microlayer and subsequent enrichment during seawaterbubble bursting. The chemical composition of the surface snowpack alsoshowed contributions from sea spray aerosol deposition. Overall, theseresults show the contribution of sea spray aerosol production from leads onboth aerosols and the surface snowpack. Therefore, if blowing snowsublimation contributed to the observed sea salt aerosol, the snow beingsublimated would have been impacted by sea spray aerosol deposition rather than upward brine migration through the snowpack. Sea spray aerosol production from leads is expected to increase, with thinning and fracturingof sea ice in the rapidly warming Arctic. 

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3. Ejection of Dust From the Ocean as a Potential Source of Marine Ice Nucleating Particles

   https://doi.org/10.1029/2020JD033073  

   Cornwell, Gavin C.; Sultana, Camille M.; Prank, Marje; Cochran, Richard E.; Hill, Thomas C. J.; Schill, Gregory P.; DeMott, Paul J.; Mahowald, Natalie; Prather, Kimberly A. (December 2020, Journal of Geophysical Research: Atmospheres)

   Abstract Oceans are, generally, relatively weak sources of ice nucleating particles (INPs). Thus, dust transported from terrestrial regions can dominate atmospheric INP concentrations even in remote marine regions. Studies of ocean‐emitted INPs have focused upon sea spray aerosols containing biogenic species. Even though large concentrations of dust are transported over marine regions, resuspended dust has never been explicitly considered as another possible source of ocean‐emitted INPs. Current models assume that deposited dust is not re‐emitted from surface waters. Our laboratory studies of aerosol particles produced from coastal seawater and synthetic seawater doped with dust show that dust can indeed be ejected from water during bubble bursting. INP concentration measurements show these ejected dust particles retain ice nucleating activity. Doping synthetic seawater to simulate a strong dust deposition event produced INPs active at temperatures colder than −13°C and INP concentrations 1 to 2 orders of magnitude greater than either lab sea spray or marine boundary layer measurements. The relevance of these laboratory findings is highlighted by single‐particle composition measurements along the Californian coast where at least 9% of dust particles were mixed with sea salt. Additionally, global modeling studies show that resuspension of dust from the ocean could exert the most impact over the Southern Ocean, where ocean‐emitted INPs are thought to dominate atmospheric INP populations. More work characterizing the factors governing the resuspension of dust particles is required to understand the potential impact upon clouds. 

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4. Numerical Representations of Marine Ice‐Nucleating Particles in Remote Marine Environments Evaluated Against Observations

   https://doi.org/10.1029/2018GL081861  

   McCluskey, C. S.; DeMott, P. J.; Ma, P. ‐L.; Burrows, S. M. (July 2019, Geophysical Research Letters)

   Abstract The abundance and sources of ice‐nucleating particles, particles required for heterogeneous ice nucleation, are long‐standing sources of uncertainty in quantifying aerosol‐cloud interactions. In this study, we demonstrate near closure between immersion freezing ice‐nucleating particle number concentration (n_INPs) observations andn_INPscalculated from simulated sea spray aerosol and dust. The Community Atmospheric Model with constrained meteorology was used to simulate aerosol concentrations at the Mace Head Research Station (North Atlantic) and over the Southern Ocean to the south of Tasmania (Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign). Model‐predictedn_INPswere within a factor of 10 ofn_INPsobserved with an off‐line ice spectrometer at Mace Head Research Station and Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign, for 93% and 69% of observations, respectively. Simulated vertical profiles ofn_INPsreveal that transported dust may be critical ton_INPsin remote regions and that sea spray aerosol may be the dominate contributor to primary ice nucleation in Southern Ocean low‐level mixed‐phase clouds. 

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5. Factors controlling the transfer of biogenic organic species from seawater to sea spray aerosol

   https://doi.org/10.1038/s41598-022-07335-9  

   Santander, Mitchell V.; Schiffer, Jamie M.; Lee, Christopher; Axson, Jessica L.; Tauber, Michael J.; Prather, Kimberly A. (December 2022, Scientific Reports)

   Abstract Ocean waves transfer sea spray aerosol (SSA) to the atmosphere, and these SSA particles can be enriched in organic matter relative to salts compared to seawater ratios. A fundamental understanding of the factors controlling the transfer of biogenic organic matter from the ocean to the atmosphere remains elusive. Field studies that focus on understanding the connection between organic species in seawater and SSA are complicated by the numerous processes and sources affecting the composition of aerosols in the marine environment. Here, an isolated ocean–atmosphere system enables direct measurements of the sea–air transfer of different classes of biogenic organic matter over the course of two phytoplankton blooms. By measuring excitation–emission matrices of bulk seawater, the sea surface microlayer, and SSA, we investigate time series of the transfer of fluorescent species including chlorophyll-a, protein-like substances, and humic-like substances. Herein, we show the emergence of different molecular classes in SSA at specific times over the course of a phytoplankton bloom, suggesting that SSA chemical composition changes over time in response to changing ocean biological conditions. We compare the temporal behaviors for the transfer of each component, and discuss the factors contributing to differences in transfer between phases. 

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