Controls of marine isoprene distributions in the western Arctic Ocean

Marine isoprene can be rapidly oxidized once released into the atmosphere, and is suggested to play a significant role in the formation of secondary organic aerosols over remote oceans. The Arctic Ocean is undergoing rapid climate change, including warming and increase in primary production, which also might influence marine isoprene production. However, our understanding of the factors and distributions of marine isoprene in the Arctic Ocean, especially in the western sector, is still limited. Herein, we investigated marine isoprene at multiple stations during the August 2024 Korean Arctic Ocean Research Expedition in the western Arctic. Seawater isoprene concentrations in the upper 100 m ranged from 11.3 to 45.5 pmol L^-1, with an average of 20.9 ± 8.2 pmol L^-1 (n = 84). The spatial distribution of isoprene showed significant variability with a general decreasing trend towards higher latitudes. Although isoprene concentrations did not show strong correlations with chlorophyll a or sea water temperature (R² = 0.236 and 0.313, respectively, p < 0.01; n = 84), phytoplankton biomass and species composition appeared to impact the distribution of marine isoprene. Especially in sea-ice covered areas, phytoplankton biomass was the dominant factor shaping isoprene concentrations. Additionally, the relatively low isoprene-producing capacity of marine phytoplankton in the western Arctic Ocean indicated that large-scale extremely high marine isoprene concentrations are unlikely to occur in this region.