382 / 2024-09-15 20:58:41
Isoprene Production and Its Driving Factors in the Northwest Pacific Ocean
Isoprene，Photochemical production， mixed layer
Session 25 - IGAC-SOLAS: Chemistry and physics at surface ocean and lower atmosphere
Abstract Accepted
Marine isoprene plays a crucial role in the formation of secondary organic aerosol within
the remote marine boundary layer. Due to scarce field measurements of oceanic isoprene and limited
laboratory-based studies of isoprene production, assessing the importance of marine isoprene on atmospheric
chemistry and climate is challenging. Calculating in-field isoprene production rates is a crucial step to
predict marine isoprene concentrations and the subsequent emissions to the atmosphere. The distribution,
sources, and dominant environmental factors of isoprene were determined in the Northwest Pacific Ocean
in 2019. The nutrient enrichment in the Kuroshio Oyashio Extension (KOE) surface seawater, driven by the
upwelling and atmospheric deposition, promoted the growth of phytoplankton and elevated the isoprene
concentration. This was confirmed by observed responses of isoprene to nutrients and aerosol dust additions
in a ship-based incubation experiment, where the isoprene concentrations increased by 70% (t = 4.417,
p < 0.001) and 35% (t = 2.387, p < 0.05), respectively. Biogenic isoprene production rates in the deck
incubation experiments were positively related to chlorophyll a, temperature, and solar radiation, with an
average production of 7.33 ± 4.27 pmol L−1 day−1. Photochemical degradation of dissolved organic matter
was likely an abiotic source of isoprene, contributing to approximately 14% of the total production. Driven by
high isoprene production and extreme physical disturbance, the KOE showed very high emissions of isoprene
of 46.0 ± 13.0 nmol m−2 day−1, which led to a significant influence on the oxidative capacity of the local
atmosphere.