Vertically-resolved source contributions to climate-relevant aerosol properties in Southern Greenlandic fjord systems

Abstract. Greenlandic fjords are rapidly changing environments where ocean, ice, land, and atmosphere interact, yet aerosol sources and their role in cloud formation remain relatively unconstrained. To address this gap, we conducted an intensive field campaign in Narsaq, Southern Greenland, during summer 2023 as part of the GreenFjord project, combining ground-based sampling with a tethered balloon (24 flights to ∼700 m). Over six weeks, we measured meteorology, aerosol number size distributions, particle and CCN number concentrations, as well as optical properties. Aerosol characteristics varied markedly in time and altitude, reflecting four main sources: fresh anthropogenic pollution, aged background aerosols from local anthropogenic and marine origins, transported biomass burning, and new particle growth events. Local pollution dominated ∼50 % of the campaign, while growth events and Canadian wildfire plumes each contributed ∼8 %; the remainder (∼34 %) reflected aged marine background aerosols. Number size distributions were typically Aitken-mode dominated, presumably due to the frequently observed growth events. Biomass burning advection, in contrast, was marked by accumulation-mode particles. During plume periods, median CCN concentrations at 0.5 % supersaturation increased by a factor of 1.7–3.7 relative to median background concentrations, while median absorption and scattering coefficients increased by factors of 1.8–4.0 and 1.4–4.8, respectively. The enhancement factors are similar to or even exceed the enhancements from local anthropogenic pollution and highlight the substantial role that long-range transported biomass burning may have in modulating aerosol–cloud–radiation interactions over southern Greenland.