Scientists have identified a previously unknown natural process in the Arctic that can cause cloud-forming particles in the atmosphere to surge by as much as 50 times in a single day — a mechanism absent from current climate models that could significantly reshape predictions of Arctic warming.
The findings, published August 5 in Nature Geoscience by an international team led by the University of Birmingham with collaborators in China and Spain, provide the first real-world evidence of a powerful particle-forming process occurring where Arctic sea ice meets open ocean.
In the marginal ice zone — the narrow region where melting sea ice meets open water — researchers observed that sunlight reacts with naturally occurring iodine, sulfur, and organic compounds released by the ocean, algae, and ice. This chemical mixture seeds the atmosphere with particles capable of influencing cloud formation. During one observed event, cloud-seeding particle concentrations jumped from about 50 to 1,500 per cubic centimeter.
The team also detected a previously unknown class of atmospheric compounds called iodine-containing oxygenated organic molecules (I-OOMs), which appear to help newly created particles grow until they are large enough to affect cloud formation. The researchers found evidence of new particle formation on more than 80% of sunny days, suggesting the phenomenon is common in this part of the Arctic.
The discovery carries significant implications for climate science. Clouds play a critical role in determining how much heat the Arctic retains or reflects. More or thicker clouds during the warming season could potentially accelerate ice melt while cooling the open ocean — a complex feedback that current models do not capture.
As Arctic sea ice continues to retreat, the marginal ice zone is becoming wider, potentially expanding the area where this particle-forming process occurs. The Arctic has warmed more than three times faster than the global average over the past 40 years, making understanding these natural emissions critical for accurate climate projections.
The researchers are now working to incorporate the process into climate models. "Our discovery is important because these new particles can influence clouds, which play a critical role in determining how much heat is retained or reflected," said corresponding author Professor Zongbo Shi of the University of Birmingham.
