Reducing CO2 emissions is a key priority to limiting catastrophic climate change, but there is scientific consensus that it will not be enough; negative carbon emissions, or carbon removal from the atmosphere, is essential alongside these carbon reduction efforts. Of the potential approaches to large-scale ocean intervention for marine Carbon Dioxide Recovery (mCDR), ocean iron fertilization (OIF) has the longest history of study. However, past OIF studies were never designed to accurately quantify the magnitude of carbon export or the durability of the resultant carbon (C) storage.  Neither was there any attempt to understand potential ecological or societal changes that might result from long-term OIF.  Thus there is little current scientific basis for determining how wise OIF might be as an mCDR approach. The steps needed to understand the efficacy and impacts of long-term OIF were considered at a recent workshop organized by the international scientific consortium Exploring Ocean Iron Solutions (ExOIS). A threshold for “effective” carbon export was defined as 1000 kg of C isolated from atmospheric contact for at least 100 years; the “centennial tonne”. Five activities were identified as needed to assess OIF from a scientific and technological perspective, along with how it might be responsibly studied and potentially deployed. These include: 1) field studies in the Northeast Pacific; 2) improved modeling for field studies, data assimilation and predictions at larger scales 3) improvements in monitoring, reporting and verification (MRV) for C, and also MRV for tracking ecological and environmental impacts (eMRV),4) developing new iron sources and their delivery, to increase efficiencies and reduce costs, and 5) understand public and community perspectives of OIF, and what governance structures might support further research and possible deployment of OIF. OIF has the potential to be economically feasible, scalable and rapidly employed, but there is urgency to decide under what conditions, if any, OIF should be implemented.
 

mCDR, iron, ocean fertilization