More Like this

1. Role of Contamination in Optimal Droplet Production by Collective Bubble Bursting

   https://doi.org/10.1029/2021GL096740  

   Néel, B.; Erinin, M. A.; Deike, L. (December 2021, Geophysical Research Letters)

   Abstract Gas bubbles bursting at the sea surface produce drops, which contribute to marine aerosols. The contamination or enrichment of water by surface‐active agents, of biological or anthropogenic origin, has long been recognized as affecting the bubble bursting processes and the spray composition. However, despite an improved understanding of the physics of a single bursting event, a quantitative understanding of the role of the physico‐chemical conditions on assemblies of bursting bubbles remains elusive. We present experiments on the drop production by millimetric, collective bursting bubbles, under varying surfactant concentration and bubble density. We demonstrate that the production of supermicron droplets (with radius larger than 35 μm) is non‐monotonic as the surfactant concentration increases. The bursting efficiency is optimal for short‐lived, sparsely distributed and non‐coalescing bubbles. We identify the combined role of contamination on the surface bubble arrangement and the modification of the jet drop production process in the bursting efficiency. 

   more » « less
2. A Mechanistic Sea Spray Generation Function Based on the Sea State and the Physics of Bubble Bursting

   https://doi.org/10.1029/2022AV000750  

   Deike, L.; Reichl, B. G.; Paulot, F. (December 2022, AGU Advances)

   Abstract Bubbles bursting at the ocean surface are an important source of ocean‐spray aerosol, with implications on radiative and cloud processes. Yet, very large uncertainties exist on the role of key physical controlling parameters, including wind speed, sea state and water temperature. We propose a mechanistic sea spray generation function that is based on the physics of bubble bursting. The number and mean droplet radius of jet and film drops is described by scaling laws derived from individual bubble bursting laboratory and numerical experiments, as a function of the bubble radius and the water physico‐chemical properties (viscosity, density and surface tension, all functions of temperature), with drops radii at production from 0.1 to 500 µm. Next, we integrate over the bubble size distribution entrained by breaking waves. Finally, the sea spray generation function is obtained by considering the volume flux of entrained bubbles due to breaking waves in the field constrained by the third moment of the breaking distribution (akin to the whitecap coverage). This mechanistic approach naturally integrates the role of wind and waves via the breaking distribution and entrained air flux, and a sensitivity to temperature via individual bubble bursting mechanisms. The resulting sea spray generation function has not been tuned or adjusted to match any existing data sets, in terms of magnitude of sea salt emissions and recently observed temperature dependencies. The remarkable coherence between the model and observations of sea salt emissions therefore strongly supports the mechanistic approach and the resulting sea spray generation function. 

   more » « less
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. 

   more » « less
4. Bubbles spray aerosols: Certitudes and mysteries

   https://doi.org/10.1093/pnasnexus/pgac261  

   Villermaux, Emmanuel; Wang, Xiaofei; Deike, Luc; Yortsos, ed., Yannis (November 2022, PNAS Nexus)

   Abstract Ocean spray aerosol formed by bubble bursting are at the core of a broad range of atmospheric processes: they are efficient cloud condensation nuclei and carry a variety of chemical, biological, and biomass material from the surface of the ocean to the atmosphere. The origin and composition of these aerosols is sensibly controlled by the detailed fluid mechanics of bubble bursting. This perspective summarizes our present-day knowledge on how bursting bubbles at the surface of a liquid pool contribute to its fragmentation, namely to the formation of droplets stripped from the pool, and associated mechanisms. In particular, we describe bounds and yields for each distinct mechanism, and the way they are sensitive to the bubble production and environmental conditions. We also underline the consequences of each mechanism on some of the many air-sea interactions phenomena identified to date. Attention is specifically payed at delimiting the known from the unknown and the certitudes from the speculations. 

   more » « less
5. Field measurements reveal exposure risk to microplastic ingestion by filter-feeding megafauna

   https://doi.org/10.1038/s41467-022-33334-5  

   Kahane-Rapport, S. R.; Czapanskiy, M. F.; Fahlbusch, J. A.; Friedlaender, A. S.; Calambokidis, J.; Hazen, E. L.; Goldbogen, J. A.; Savoca, M. S. (November 2022, Nature Communications)

   Abstract Microparticles, such as microplastics and microfibers, are ubiquitous in marine food webs. Filter-feeding megafauna may be at extreme risk of exposure to microplastics, but neither the amount nor pathway of microplastic ingestion are well understood. Here, we combine depth-integrated microplastic data from the California Current Ecosystem with high-resolution foraging measurements from 191 tag deployments on blue, fin, and humpback whales to quantify plastic ingestion rates and routes of exposure. We find that baleen whales predominantly feed at depths of 50–250 m, coinciding with the highest measured microplastic concentrations in the pelagic ecosystem. Nearly all (99%) microplastic ingestion is predicted to occur via trophic transfer. We predict that fish-feeding whales are less exposed to microplastic ingestion than krill-feeding whales. Per day, a krill-obligate blue whale may ingest 10 million pieces of microplastic, while a fish-feeding humpback whale likely ingests 200,000 pieces of microplastic. For species struggling to recover from historical whaling alongside other anthropogenic pressures, our findings suggest that the cumulative impacts of multiple stressors require further attention. 

   more » « less