Evaluating natural aerosol sources from the Arctic Ocean during the onset of sea ice melt

• DOI: 10.5194/egusphere-egu25-17925
• Publication Date: 2025-03-15T04:54:01Z
• Authors: Julia Kojoj; Gabriel Pereira F...; Camille Mavis; Jessie Creamean; Fredrik Mattsson; Lovisa Nilsson; Jennie Spicker Sc...; Kouji Adachi; Tina Santl-Temkiv; Erik Ahlberg; Claudia Mohr; Ilona Riipinen; Paul Zieger

Aerosol-cloud interactions remain one of the most significant challenges in accurately estimating human-induced radiative forcing, as well as projecting the future climate. To address this uncertainty, establishing the baseline levels of natural aerosols in various environments is crucial. The polar regions are ideal locations for studying natural aerosols due to their distances from anthropogenic influences, yet observations in these regions are relatively limited. Specifically, the role of oceans and sea ice in controlling aerosol concentrations, influencing cloud formation, and determining cloud phase remains unclear. A key component is biological aerosol particles that participate in the formation and microphysical modulation of Arctic mixed-phase clouds. Yet, many questions regarding their Arctic sources, emission processes, and ice nucleating properties remain.We present a detailed study of potential natural sources of aerosols in the high Arctic over the pack ice during the ARTofMELT expedition (May–June 2023). We collected samples of snow, sea ice, seawater, and the sea-surface microlayer (SML) and utilized the comprehensive aerosol instrumentation setup on-board to analyze them immediately after collection for their chemical, microphysical, and fluorescent properties. After the expedition, further analysis of the samples was conducted including measurements of ice-nucleating properties and biological cell quantification.Our results show that during the late Arctic spring, heightened biological activity in the seawater and the SML increased emissions of fluorescent primary biological aerosol particles (confirmed by increased cell count) and organic-coated sea salt particles. However, concentrations of ice-nucleating particles in liquid samples did not follow the same trend. We will present the clear distinctions found in the biological, chemical, and physical properties of all sample types, and the effect of salinity on the aerosolization process and ice nucleating activity. These results provide valuable information for future studies aimed at improving the source attribution of natural Arctic aerosols, helping to reduce uncertainties in their representation in models, and understanding their influence on Arctic mixed-phase clouds. This work is currently in discussion at Freitas et al. (2024).Freitas GP, Kojoj J, Mavis C, Creamean J, Mattsson F, Nilsson L, Schmidt JS, Adachi K, Šantl-Temkiv T, Ahlberg E, Mohr C. A comprehensive characterisation of natural aerosol sources in the high Arctic during the onset of sea ice melt. Faraday Discussions. 2024. DOI: 10.1039/D4FD00162A