Clouds in the Arctic are among the biggest unanswered questions in climate science, with particular uncertainty about how the minute particles found in the air, known as aerosols, drive cloud formation and how clouds affect the number of aerosols as the region warms.
One key question is the significance of aerosols originating in atmospheric trace gases. As they grow, these particles can turn into cloud condensation nuclei, meaning particles on whose surface water vapor condenses into droplets.
Three Arctic Regimes
According to the study, the Arctic is divided into three regimes: the High Arctic, the Maritime Arctic, and the Continental Arctic. The High Arctic stands out from the other two because of its permanent ice cover, which affects aerosol formation.
The study estimates that, as the climate becomes warmer, the number of naturally formed aerosols and cloud condensation nuclei is likely to increase in the ice-covered High Arctic. In contrast, a decline is likely in the open waters of the Maritime Arctic.
In the Continental Arctic, the outcome depends less on global warming than on changes in human-generated air pollution in the coming decades.
Nanoparticles Are Difficult to Measure
Although the relevance of aerosols for cloud formation has been known for decades, knowledge on the formation of the particles themselves has accumulated more slowly. The reason is technical: detecting newly formed nanometer-sized particles is difficult. In addition, using measuring equipment in the demanding conditions of the Arctic poses a challenge.
The recently published study is based on data on the size distribution of aerosols collected over more than 20 years. The data were compiled from eight measuring stations and several research expeditions across the Arctic.
The aerosol data were paired with satellite observations and analyzed using methods developed for the study, making it possible to distinguish differences within the Arctic for the first time.
The researchers point out that the study does not yet provide a definitive answer to how aerosols shape the Arctic climate.
“The question is not just about whether the Arctic will get cloudier. You also have to ask where and how much?” says lead author, Doctoral Researcher Samuel Chua of the University of Helsinki.
The study was headed by researchers from the University of Helsinki’s Institute for Atmospheric and Earth System Research (INAR) in cooperation with several research institutes, including the Finnish Meteorological Institute.
“This study really emphasizes the importance of continuous, long-term aerosol records at northern locations, such as the Finnish stations in Värriö and Pallas in Lapland,” says Professor Katrianne Lehtipalo from the University of Helsinki and the Finnish Meteorological Institute.
“Only with a solid foundation of observational data can we build and use modern analytical tools, including AI-assisted satellite analyses.”
The article Contrasting aerosol–cloud feedbacks across a warming Arctic was published in Nature Geoscience.
