The Influence of Natural, Anthropogenic, and Wildfire Sources on Iron and Zinc Aerosols Delivered to the North Pacific Ocean

Our investigation of stable isotope ratios of iron (and zinc) aerosols from the North Pacific, paired with aerosol enrichment factors and iron deposition model (CAM6) output shows that Asian Outflow aerosols (north of 20°N) comprise natural and human-derived iron from East Asia, but Equatorial Pacific aerosols (south of 20°N) are strongly influenced by Californian wildfires during the low dust-season/North American wildfire season. Previously, aerosols with 'heavy' isotope signatures have been a topic of research, but not yet constrained to a specific source. Wildfire iron was thought to have a 'light' isotope signature because of plants, but here, based on observations and model simulations, we argue that organic-rich Californian soil, entrained during wildfires, is what contributes 'heavy' iron to the aerosols.

Reference: Bunnell, Z., Sieber, M., Hamilton, D., et al. (2025). The Influence of natural, anthropogenic, and wildfire sources on iron and zinc aerosols delivered to the North Pacific Ocean. Geophys. Res. Lett., 52(3), e2024GL113877. https://doi.org/10.1029/2024GL113877