Ocean fertilization with iron: effects on climate and air quality

It is well known that iron fertilization can increase primary production and hence CO₂ drawdown over a significant fraction of the oceans. What is less well established is the extent to which this leads to long-term sequestration of carbon to the deep oceans, and to feedbacks to the atmosphere arising from increased biological activity. In this note results for changes in trace gas concentrations during an iron addition experiment in the Southern Ocean are presented. They demonstrate that a complex situation exists; some gases (DMS, CH₃I, CHBr₂Cl) show increases in concentration following fertilization with iron while others show no change (CH₃ONO₂, CH₂ClI) or even a decrease (CHBr₃). The concomitant effects on air—sea fluxes of these gases are potentially important for climate and atmospheric composition.