Regulation of short-lived halocarbon distributions and emissions by the Indonesian Throughflow in the Eastern Indian Ocean

Short-lived brominated and iodinated methanes, such as bromoform (CHBr₃), dibromomethane (CH₂Br₂), and methyl iodide (CH₃I), have significant implications for the halogen cycle, atmospheric chemistry, and climate change. Despite their importance, the spatial variability and emission patterns of these halocarbons originating from unique marine environments remain poorly understood. Here, we investigate the response of CH₃I, CHBr₃, and CH₂Br₂ to physical and biological drivers in the Eastern Indian Ocean, a region significantly influenced by the Indonesian Throughflow (ITF). We observe that concentrations of CH₃I, CHBr₃, and CH₂Br₂ are significantly higher in the northern region than in the southern region within the ITF-influenced area, resulting in emission fluxes that are 1.5 to 2.0 times greater than those in the southern region. This enhanced emission is driven by the interaction between nutrients and biological processes. Such interplay is boosted by the warm ITF, with the most pronounced effects observed in the northern ITF-influenced regions. Additionally, we uncover that the nutrient supply at the convergence front of water masses, driven by eddies and upwelling, serves as a key driver for the production of CH₃I, CHBr₃, and CH₂Br₂. This research highlights the significant contribution of unique marine dynamic processes to atmospheric CH₃I, CHBr₃, and CH₂Br₂, thereby deepening our understanding of their oceanic releases and atmospheric budgets.