Organic matter carried in rivers to the Russian part of the Arctic Ocean may be creating more clouds and keeping the region cooler, a new study has found.
In a new paper published in Communications Earth & Environment , an international team of researchers, including atmospheric specialists from the University of Birmingham, examined an understudied region of the Arctic Circle which includes the Siberian region of Russia, to understand how aerosol formation, which is essential for cloud formation, was influenced by conditions in the region.
The researchers investigated the origins of Arctic clouds, finding that organic matter carried from rivers into the Arctic basin, such as rotting leaves, soil, nutrients and living biological material, releases gases that form tiny particles in the air, known as aerosols. These particles act as the essential 'seeds' for cloud formation, allowing water vapour to condense around them and create cloud droplets.
Higher levels of aerosols in the air create clouds that are longer lasting and brighter. When the number of cloud droplets is high, the droplets are smaller, lighter, and shinier, making them less efficient at forming rain.
The findings from the paper suggest that the Russian region affects the Arctic climate in previously unknown ways. Nine years of data taken from the Tiksi meteorological observatory in Northern Siberia, which sits on the Lena River Delta, was combined with satellite mapping. The research team analysed the resulting data to track the formation of aerosol particles in the air when air masses travelled over water rich in biological matter from river runoff.
The team found that aerosol particles affected by this river runoff formed 300% faster, and grew 60% faster in the study. The resulting increase in aerosol particles significantly increased the ability of bright, long-lasting and cooling clouds to form.
Cold spot for research
Biological matter in river runoff increasing the chances of cloud formation in the Arctic Circle is an important discovery for improving climate modelling in the North Pole.
The Arctic is heating four times faster than other parts of the world, and climate scientists use models to understand how the Arctic Circle, which is seeing a trend towards less ice formation year on year, will behave as global warming continues.
Dr James Brean from the University of Birmingham and first author of the paper said: "Clouds play an important role in regulating Arctic temperature, yet we have cold spots in our knowledge of how they form in large areas of the Arctic. Our new study shows that terrestrial organic matter carried by rivers is a key ingredient for seeding these clouds. By identifying this natural source, we can build more accurate climate models to predict when the Arctic may become ice-free."
Dr Manuel Dall'Osto from the Spanish National Research Centre CSIC, and corresponding author of the paper said: "When rivers flow into the Arctic Ocean, they carry 'dissolved organic matter'. Once this mix hits the ocean, it helps create tiny new particles in the air called aerosols. These little particles act like seeds, with water vapour holding on to them and then forming clouds. Clouds can either trap heat or reflect sunlight, regulating the Arctic temperature. As the Arctic warms, more rivers flow into the sea, meaning more particles, more clouds, and a potential shifting climate we largely overlooked in these regions. Our study shows how international collaborations are important to understand our changing climate."
Full citation: Brean, J., et al, 2026, Continental river runoff enhances atmospheric aerosol formation over the Arctic Ocean. Communications Earth & Environment, DOI: 10.1038/s43247-025-02986-8
