1. Department of Physics, National University of Ireland, Galway, Ireland
2. Division of Atmospheric Sciences, Department of Physical Sciences, P.O. Box 64, FIN-00014, University of Helsinki, Helsinki, Finland
3. Departments of Environmental Science and Engineering and Chemical Engineering, California Institute of Technology, 210-41, 1200 E. California Boulevard, Pasadena, USA
4. Finnish Institute for Occupational Health, Topeliuksenkatu 41a, FIN-00250, Helsinki, Finland
5. Helsinki Polytechnic Technology, PL 4020, FIN-00099, Helsinki, Finland
6. Institute of Spectrochemistry and Applied Spectroscopy, 44139 Dortmund, Germany

Correspondence to: Colin D. O'Dowd^1,2 Correspondence and requests for materials should be addressed to C.D.O'D. (e-mail: Email: colin.odowd@cmas.demon.co.uk).

Abstract

The formation of marine aerosols and cloud condensation nuclei—from which marine clouds originate—depends ultimately on the availability of new, nanometre-scale particles in the marine boundary layer. Because marine aerosols and clouds scatter incoming radiation and contribute a cooling effect to the Earth's radiation budget¹, new particle production is important in climate regulation. It has been suggested that sulphuric acid—derived from the oxidation of dimethyl sulphide—is responsible for the production of marine aerosols and cloud condensation nuclei. It was accordingly proposed that algae producing dimethyl sulphide play a role in climate regulation², but this has been difficult to prove and, consequently, the processes controlling marine particle formation remains largely undetermined^{3, 4}. Here, using smog chamber experiments under coastal atmospheric conditions, we demonstrate that new particles can form from condensable iodine-containing vapours, which are the photolysis products of biogenic iodocarbons emitted from marine algae. Moreover, we illustrate, using aerosol formation models, that concentrations of condensable iodine-containing vapours over the open ocean are sufficient to influence marine particle formation. We suggest therefore that marine iodocarbon emissions have a potentially significant effect on global radiative forcing.

1. Department of Physics, National University of Ireland, Galway, Ireland
2. Division of Atmospheric Sciences, Department of Physical Sciences, P.O. Box 64, FIN-00014, University of Helsinki, Helsinki, Finland
3. Departments of Environmental Science and Engineering and Chemical Engineering, California Institute of Technology, 210-41, 1200 E. California Boulevard, Pasadena, USA
4. Finnish Institute for Occupational Health, Topeliuksenkatu 41a, FIN-00250, Helsinki, Finland
5. Helsinki Polytechnic Technology, PL 4020, FIN-00099, Helsinki, Finland
6. Institute of Spectrochemistry and Applied Spectroscopy, 44139 Dortmund, Germany

Correspondence to: Colin D. O'Dowd^1,2 Correspondence and requests for materials should be addressed to C.D.O'D. (e-mail: Email: colin.odowd@cmas.demon.co.uk).