| Summary: | Mixed phase clouds (MPC) play an important role in the Arctic climate through their interaction with radiation. The amount of ice in MPCs determines their microphysical properties and is one of the main sources of uncertainties in models. One key parameter driving the ice content in MPC’s is the amount of available ice nucleating particles (INP) in the Arctic atmosphere. To better represent INP in models, observations that quantify and describe the properties of INP and appoint the respective sources are urgently needed. One contributor to INP in the Arctic are bioaerosols, such as bacteria or spores, which are regarded as efficient INP at high temperatures. However, their sources and presence in the Arctic are poorly understood. Within this work, we report long-term observations of bioaerosols and INP which took place at the Zeppelin Observatory, an Arctic mountain site, in the archipelago of Svalbard. Bioaerosols were identified with single-particle spectroscopic technique and were confirmed by bioaerosol tracers as well as electronic microscopy imaging. Their seasonal cycle showed elevated concentrations in summer that followed several key parameters such as ambient temperature, vegetation and snow cover, linking bioaerosols to potential local terrestrial sources. INP followed a similar seasonal cycle, exhibiting elevated concentrations of high-temperature INP in summer that closely matched the bioaerosol abundance (concentrations between 10 -3 -10 -1 L-1). The high-temperature INP organic fraction reached levels above 90% in summer, strengthening the link to bioaerosols. In summary, we present the first direct links between bioaerosols and INP, along with their seasonality and quantification.
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