Summertime Primary and Secondary Contributions to Southern Ocean Cloud Condensation Nuclei

• Published in: Scientific Reports
• Main Authors: Fossum, Kirsten N., Ovadnevaite, Jurgita, Ceburnis, Darius, Dall’osto, Manuel, Marullo, Salvatore, Bellacicco, Marco, Simó, Rafel, Liu, Dantong, Flynn, Michael, Zuend, Andreas, O’dowd, Colin
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Antarc*; Antarctic; Antarctica; Southern Ocean
• Online Access: https://research.manchester.ac.uk/en/publications/631e1750-1e08-4298-9f52-2bf313568dc5; https://doi.org/10.1038/s41598-018-32047-4; http://www.nature.com/articles/s41598-018-32047-4

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 (PM 1 ) 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%.