In summer 2019, unusually high aerosol concentrations were measured in the Arctic, extending through the troposphere and stratosphere up to 16 km. Using multiple instruments and models, aerosol particles were linked to wildfires, volcanic eruptions, and anthropogenic pollution. The aerosol consisted of spherical, fine-mode, weakly absorbing particles, which significantly reduced direct solar radiation. This combined approach improves understanding of Arctic aerosol events and climate processes.