Iodine cycle in polar regions and its impact on aerosols and clouds

Atmospheric iodine, dominated by ocean emissions, is important in atmospheric chemistry as iodine is a very efficient ozone depleting substance in the atmosphere, and can form new particles that can grow to cloud condensation nuclei (CCN) sizes, thereby establishing a direct link between iodine emissions and impacts on climate. This CATCH & SOLAS seminar will highlight the recent understanding and future challenges of iodine cycling in various environments, such as the polar regions and remote marine boundary layer, and the roles of iodine in driving marine secondary aerosol formation.

08:00-10:00 UTC, Monday, 22 April 2024
Cryosphere and Atmospheric Chemistry (CATCH) & SOLAS Early Career Scientist Committee (ECSC)
Hélène Angot (CNRS, Institut des Géosciences de l'Environnement, France)
Andrea Baccarini (Laboratory of Atmospheric Processes and Their Impacts, Switzerland)
Yee Jun Tham (Sun Yat-sen University, China)


Anoop S. Mahajan
Indian Institute of Tropical Meteorology, India
Title: Iodine chemistry in the atmosphere - evolution of our understanding
Abstract: Iodine chemistry plays an important role in the atmosphere, affecting various chemical cycles and contributing to new particle formation. After first observations of organic iodine compounds, which showed the potential role iodine plays in the atmosphere, observations over the last two decades have shown that reactive inorganic iodine compounds are found in almost all environments such as the polar regions, remote marine boundary layer, free troposphere and even in the stratosphere. This talk will summarise the observations and identify key areas where we need more information. The talk will also explore the impact of iodine on atmospheric chemistry, highlighting the key roles and uncertainties that exist.
Xu-Cheng He
University of Cambridge, UK / University of Helsinki, Finland
Title: Iodine and sulfur oxoacids as the key driving marine secondary aerosol formation
Abstract: Clouds in marine and polar atmospheres play a pivotal role in shaping climate dynamics through intricate cloud-radiation interactions. Of particular significance are secondary aerosols, stemming from gas precursors, which act as potential nuclei for cloud droplets, exerting influence on cloud reflectivity and lifespan. This, in turn, has indirect impacts on climate. Despite their critical impact, the formation processes of marine and polar aerosols remain insufficiently explored due to experimental and logistical challenges. This presentation will present evidence drawn from field observations and laboratory experiments, underscoring the importance of iodine and sulfur species as key aerosol sources in polar and marine atmospheres. Our field observations expose the presence of HIO3 in diverse environments, including polar regions, boreal forests, marine sites, and urban areas. By combining global observations and laboratory experiments, we reveal the potential widespread involvement of iodic acid and iodous acid in marine secondary aerosol formation, challenging the traditional association of iodine aerosols solely with mid-latitudinal regions.