[A-AS11] Atmospheric Chemistry

[AAS11-16] The underappreciated role of anthropogenic sources in atmospheric soluble iron flux to the Southern Ocean

*Mingxu Liu¹, Hitoshi Matsui¹ (1.Nagoya University)

Keywords:iron oxides, global aerosol simulations, Southern Ocean, anthropogenic activities

The atmospheric deposition of soluble (bioaccessible) iron enhances ocean primary productivity and subsequent atmospheric CO₂ sequestration in iron-limited ocean basins, especially the Southern Ocean. While anthropogenic sources have been recently suggested to be important in some northern hemisphere oceans, the role in the Southern Ocean remains ambiguous. In this study, we constrain the atmospheric cycle of anthropogenic iron oxides using new aircraft measurements and global aerosol model simulations. The deposition fluxes of soluble iron from the atmosphere to the Southern Ocean are estimated under present-day and future scenarios. First, by comparing multiple model simulations with the aircraft observations for anthropogenic iron, we show that anthropogenic soluble iron deposition flux to the Southern Ocean could be underestimated by more than a factor of ten in previous modeling estimates. Our improved estimate for the anthropogenic iron budget then enhances its contribution to the soluble iron deposition in the Southern Ocean from about 10% to 60%, implying a dominant role of anthropogenic sources. We predict that anthropogenic soluble iron deposition in the Southern Ocean is reduced substantially (30% to 90%) by the year 2100, and play a major role in the future evolution of atmospheric soluble iron inputs to the Southern Ocean.