Biogeochemical Controls on Volatile Sulfur Compounds in the Kuroshio‐Oyashio Confluence Region

Abstract Marine‐derived volatile sulfur compounds (VSCs) play a critical role in global climate regulation and the sulfur biogeochemical cycle. To characterize their biogeochemical dynamics, a comprehensive investigation on VSCs, including dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS 2 ), was conducted in the upper seawater and the overlying atmosphere in the Kuroshio‐Oyashio confluence region. The average concentrations of DMS, OCS and CS 2 were 1.03 ± 1.40, 0.075 ± 0.042, 0.029 ± 0.024 nmol L −1 in seawater, and 125.9 ± 58.9, 497.9 ± 157.1, 67.4 ± 56.9 pptv in the atmosphere, respectively. Mean sea‐to‐air fluxes of DMS, OCS and CS 2 were 5.67 ± 6.20, 0.151 ± 0.273, and 0.125 ± 0.148 μmol m −2 d −1 , respectively. The elevated OCS and CS 2 in subsurface waters of the Kuroshio Extension (KE) were attributed to phytoplankton abundance and temperature‐dependent hydrolysis. The production of DMS, as the chemical signaling molecule and antioxidant, was promoted in the KE and eddy‐active regions in warm but oligotrophic conditions. Co‐occurrence of high DMS and CS 2 concentrations with elevated chlorophyll levels in upper waters of the Oyashio Current highlighted the pivotal role of phytoplankton in the production of DMS and CS 2 . Notably, the edges of oceanic eddies were observed as hotspots for OCS and CS 2 . Mixing ratios of VSCs in the atmosphere were comprehensively modulated by sea‐air interactions, air mass transport, and oxidation processes. These findings provide valuable insights into the complex interplay between biological and physical processes that govern the biogeochemistry of VSCs in dynamic oceanic environments.