Ice Formation Potential of Field-Collected Marine Biogenic Particles
Abstract
Marine biogenic particles composed mainly of sea salt and organic material aerosolized from a mesocosm in laboratory experiments have recently been found to act as ice nuclei. How these particles relate to those collected from sea spray under ambient conditions in the field is unknown. This study reports on the heterogeneous ice nucleation potential of particles collected during the marine aerosol characterization experiment (MACE) on the south shore of Long Island, New York. Ambient aerosol size distributions were measured and particles were collected on hydrophobically coated substrates and subsequently used for ice nucleation experiments using an ice nucleation cell coupled to an optical microscope. This technique allows detection of ice formation for temperatures between 200 and 273 K and for relative humidity with respect to ice (RHice) from 100% up to water saturation. Individual ice nucleating particles were identified for subsequent chemical and physical characterization using both X-ray and electron micro-spectroscopic techniques. Concentrations of bacteria, viruses, and transparent exopolymer particles (TEP) in the bulk seawater, sea-surface microlayer (SML), and in sea spray were determined using established methods and related to airborne sea spray particles and their ice nucleation potential. Onshore aerosol size distribution measurements taken at 5 m height and 10 m away from the breaking waves, revealed a peak maximum at 100 nm and Ntot = 6.8 x 10^2 cm^-3. Bacterial, viral, and TEP were found to be enriched in the SML. Ambient particles collected during MACE were found to nucleate ice efficiently, e. g. at 215 K, ice nucleation occurred on average at 125% RHice. Results of aerosol size distributions and ice nucleation efficiencies are compared to laboratory bubble bursting experiments in which natural seawater was used. The goal of this study is to understand the connection between sea spray aerosolization and atmospheric ice cloud formation and to provide physically and chemically based descriptions of ice nucleation for implementation in aerosol-cloud interaction models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A11D0091C
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE Aerosols and particles;
- 0312 ATMOSPHERIC COMPOSITION AND STRUCTURE Air/sea constituent fluxes;
- 3311 ATMOSPHERIC PROCESSES Clouds and aerosols;
- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE Cloud physics and chemistry