Scientists Find a Hidden Arctic Process That Can Multiply Cloud-Seeding Particles 50-Fold

Scientists have identified a previously unknown natural process occurring where Arctic sea ice meets open ocean that can cause a surge in the number of particles able to seed clouds. The findings, published August 5 in the journal Nature Geoscience, come from a team led by the University of Birmingham with collaborators in China and Spain.

The process involves naturally occurring iodine, sulfur compounds such as dimethylsulfide, and organic compounds released by marine life and sea ice. When sunlight reacts with this mixture near the ice edge, it can seed the atmosphere with new particles. Researchers recorded the concentration of cloud-forming particles in one part of the ice edge climbing from about 50 to 1,500 per cubic centimeter within a single day, and found new particle formation on more than 80% of sunny days during their measurements.

The team, aboard the research ship RRS Discovery around Greenland and the Davis Strait in 2022, also identified a previously unrecorded class of compounds, iodine-containing oxygenated organic molecules (I-OOMs), that help the newly formed particles grow large enough to seed clouds. "These newly identified compounds help small particles grow into larger particles that can seed clouds," said co-author Dr. James Brean, Assistant Professor in Atmospheric Science at the University of Birmingham, adding it is the first time such molecules have been observed.

As the Arctic warms, more sea ice melts and the biologically active ice-edge zone widens, potentially increasing the area where the process occurs. "The Arctic has warmed more than three times faster than the global average over the past 40 years," said Zongbo Shi, Professor of Atmospheric Biogeochemistry at Birmingham, who led the study. Current climate models do not include this mechanism, and researchers are now working to add it so its effect on Arctic warming can be assessed.