Modeling of atmospheric transport and deposition of iron to the oceans

Today it is widely accepted that atmospheric transport and deposition of mineral dust from continental regions plays an important role in oceanic iron (Fe) supply. The major challenge for oceanic biogeochemists is the conversion of dust deposited fluxes of Fe to those that are bioavailable, i.e., fluxes that can directly affect marine ecosystem productivity. Formation of soluble Fe in ambient aerosols is very complex process. Iron solubility can be strongly influenced by properties of the overall system (e.g. temperature, UV light), the composition of the solution phase (e.g. pH, redox potential, concentration of acids, reductants and complexing agents) and properties of the minerals (e.g. stoichiometry, crystal chemistry, crystal habit and presence of defects or guest ions). Dissolved Fe concentrations in ambient aerosols can be further controlled by cloud cycling of aerosols and complex photochemical/chemical cycling between highly insoluble ferric, Fe(III) and relatively more soluble ferrous, Fe(II) complexes. This talk will give an overview of prognostic and diagnostic modeling approaches for chemical evolution of Fe in ambient aerosols and fluxes of dissolved Fe to different parts of the global ocean. The relative importance of different sources and mechanisms in Fe solubilization during atmospheric transport of aerosols will also be addressed. Results taken from in-situ and laboratory experiments will be used to illustrate the existing uncertainty areas in the modeling field. Some insights will be shared on the need and direction of future research.