Summertime Primary and Secondary Contributions to Southern Ocean Cloud Condensation Nuclei

• Main Authors: Kirsten N. Fossum, Jurgita Ovadnevaite, Darius Ceburnis, Manuel Dall’Osto, Salvatore Marullo, Marco Bellacicco, Rafel Simó, Dantong Liu, Michael Flynn, Andreas Zuend, Colin O’Dowd
• Format: Article
• Language: English
• Published: Nature Publishing Group 2018-09-01
• Series: Scientific Reports
• Subjects: Peak Supersaturation; Aerosol Population; Cloud Droplets; Scanning Mobility Particle Sizer (SMPS); Aitken Mode
• Online Access: https://doi.org/10.1038/s41598-018-32047-4

Abstract Atmospheric aerosols in clean remote oceanic regions contribute significantly to the global albedo through the formation of haze and cloud layers; however, the relative importance of ‘primary’ wind-produced sea-spray over secondary (gas-to-particle conversion) sulphate in forming marine clouds remains unclear. Here we report on marine aerosols (PM1) over the Southern Ocean around Antarctica, in terms of their physical, chemical, and cloud droplet activation properties. Two predominant pristine air masses and aerosol populations were encountered: modified continental Antarctic (cAA) comprising predominantly sulphate with minimal sea-salt contribution and maritime Polar (mP) comprising sulphate plus sea-salt. We estimate that in cAA air, 75% of the CCN are activated into cloud droplets while in mP air, 37% are activated into droplets, for corresponding peak supersaturation ranges of 0.37–0.45% and 0.19–0.31%, respectively. When realistic marine boundary layer cloud supersaturations are considered (e.g. ~0.2–0.3%), sea-salt CCN contributed 2–13% of the activated nuclei in the cAA air and 8–51% for the marine air for surface-level wind speed < 16 m s−1. At higher wind speeds, primary marine aerosol can even contribute up to 100% of the activated CCN, for corresponding peak supersaturations as high as 0.32%.