Atmospheric Chemistry and Climate Group
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Recent work on iodine

(Photograph by Andrea Baccarini)

New atmospheric particle formation is one is the largest uncertainties in climate simulations. Although it is known for the last two decades that iodine oxides form new particles in the lower atmosphere, its inclusion in atmospheric models is hindered by a lack of understanding of the first steps of the photochemical gas-to-particle conversion mechanism.

In a recent study (Nature Communications, 2020: https://www.nature.com/articles/s41467-020-18252-8), combined laboratory experiments, theory and modelling revealed the mechanism that connects oceanic iodine emissions and atmospheric particle formation. In a recent study published in Nature Communications (https://doi.org/10.1038/s41467-020-18551-0), it has been reported that iodine is the main source of new particles in the central Arctic. The observations were made during an expedition to the central Arctic in 2018 (Microbiology-Ocean-Cloud-Coupling in the High Arctic, MOCCHA) on board the Swedish icebreaker Oden. The results not only highlight the remarkable capacity that iodine oxides have to form new particles but also show that these new particles grow to cloud condensation nuclei (CCN) sizes, thereby establishing a direct link between iodine emissions and CCN in the remote region. This first observations will be confirmed and extended by those in the ongoing MOSAiC expedition (https://mosaic-expedition.org/), which is close to completion.

These very recent results from laboratory experiments and fieldwork are climatically relevant since the global iodine emissions have tripled in the last 70 years following the increase in anthropogenic ozone pollution (https://www.nature.com/articles/s41467-018-03756-1), and it is expected that this increase will continue in the future (https://www.nature.com/articles/s41558-019-0675-6). Hence, one could think that the role of iodine in new particle formation and CCN could also increase in the future atmosphere.

 

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