Contrasting aerosol-cloud feedbacks across a warming Arctic

In the rapidly warming Arctic, the feedback between aerosols and clouds is a major source of uncertainty in projections of future climate. One source of this uncertainty is the role of new particle formation, which produces aerosol particles that can subsequently grow into cloud condensation nuclei, thereby influencing Arctic cloud formation. Here harmonized field aerosol observations across the Arctic spanning 2003-2024, alongside satellite-derived data, were analysed to quantify trends in new particle formation and estimate their climatic implications across the Arctic region. Three distinct aerosol regimes, with contrasting contributions of new particle formation to cloud condensation nuclei populations, were identified: the High Arctic, the Maritime Arctic and the Continental Arctic. In these three regimes, temperature-sensitivity estimates based on the intermediate future warming scenario suggest that by 2090-2100, cloud condensation nuclei concentrations associated with new particle formation activity could increase by 3-16% in the High Arctic but decline by 15-31% in the Maritime Arctic. These contrasting estimates indicate that aerosol-cloud feedbacks will evolve differently across the mosaic of Arctic aerosol regimes.