[A-CG41] Biogeochemical linkages between the surface ocean and atmosphere

[ACG41-05] Ship-based Observation of Ice-Nucleating Particles over the Western North Pacific, Bering Sea, and Arctic Ocean: Importance of Siberian forest fires as their source

*Fumikazu Taketani¹, Yutaka Tobo^2,3, Takuma Miyakawa¹, Masayuki Takigawa¹, Chunmao Zhu¹, Yugo Kanaya¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.National Institute of Polar Research, 3.SOKENDAI)

Keywords:Ice-nucleating particles, Auto-fluorescent particles, Ship-based observation, Forest fire, Northern High latitude, Open ocean

Ice-nucleating particles (INPs) have a significant influence on aerosol-cloud-precipitation interactions on regional and global scales. However, information regarding INPs over the open ocean, particularly at high latitudes, remains insufficient. In this study, we investigated the properties and origins of INPs over the western North Pacific to the Arctic Ocean through ship-borne observations conducted in the early autumn of 2016. The number concentrations of INPs (N_INPs) active at temperatures >-25°C (N_{INPs(T>25°C)}) and >-15°C (N_{INPs(T>-15°C)}) varied from 0.034 – 41.2 L^-1 and < 0.0005 – 0.11 L^-1, respectively, and those over the Arctic Ocean (>70°N) were lowest. Comparisons of the observed N_INPs variation with chemical compositions and auto-fluorescent properties of aerosol particles indicated that N_{INPs(T>-25°C)} and N_{INPs(T>-15°C)} were influenced by terrestrial and biological materials, respectively. We further observed anomalously high N_{INPs(T>-25°C)} and N_{INPs(T>-15°C)} over the Bering Sea (- 60°N). Aerosol composition and backward trajectory analyses indicated that particles containing soil and biogenic components, long-range transported from Siberian forest fires, significantly contributed to the observed high N_INPs over the ocean. These results suggest a substantial role of forest fires in the supply of INPs to the northern high-latitude oceans.