Roles of marine biota in the formation of atmospheric bioaerosols, cloud condensation nuclei, and ice-nucleating particles over the North Pacific Ocean, Bering Sea, and Arctic Ocean

Abstract. We investigated the association of marine biological indicators (polysaccharides and protein-like gel particles, Chl-a) with the formation of fluorescent aerosol particles, cloud condensation nuclei (CCN), and ice-nucleating particles (INPs) over the North Pacific Ocean, Bering Sea, and Arctic Ocean during September–November 2019. The abundance of bioindicators was high in the North Pacific Ocean and the Bering Sea (e.g., up to 1.3 mg m⁻³ of Chl-a), suggesting high biological activity known as the autumn bloom. In the North Pacific Ocean, particles were characterized by high mass fractions of organics and sulfate with predominance of terrestrial air masses. Conversely, in the Bering Sea and the Arctic Ocean, particles were characterized by high mass fractions of sea salt and sulfate with predominance of maritime air masses. The averaged CCN concentration at 0.4 % supersaturation ranged from 99–151, 43–139, to 36 cm⁻³ over the North Pacific Ocean with terrestrial influences, over the Bering Sea with marine biogenic influences, and over the Arctic Ocean with marine influences, respectively, and the corresponding range of hygroscopicity parameter ĸ was 0.17–0.60, 0.42–0.68, and 0.67, respectively. The averaged INP concentration (N_INP) measured at temperatures of −18 and −24 °C with marine sources was 0.01–0.09 and 0.1–2 L⁻¹, respectively, and that over the Arctic Ocean was 0.001–0.016 and 0.012–0.27 L⁻¹, respectively. When marine sources were dominant, fluorescent bioaerosols were strongly correlated with all bioindicator types (R: 0.81–0.88) when considering the wind-uplifting effect from the sea surface to the atmosphere. Correlations between N_INP measured at −18 and −24 °C and all bioindicator types (R: 0.58–0.95 and 0.79–0.93, respectively) and between N_INP and fluorescent bioaerosols (R: 0.50 and 0.60, respectively) were also positive, suggesting that marine bioindicators contributed substantially as sources of bioaerosols and cloud formation.