Carbon dioxide removal through manipulation of the ocean carbonate system: Fundamentals, opportunities, and challenges

This is the authors' abstract. We don't add key points for this paper.

Carbon removal from Earth's atmosphere will be required in the coming decades as a supplement to decarbonization to meet key climate goals. The scale of intervention is forecast to be massive—on the order of 1–10 Gt of carbon dioxide (GtCO 2 = 10 9 tons of CO 2 ) per year. Because of the capacity of Earth's oceans to transport and store vast amounts of carbon, there has been strong interest in modifying the marine carbonate system to foster greater uptake and long-term storage of carbon in the oceans. Here, we review electrochemical, mineral-based, and ecosystem-based approaches toward intentional modification of the ocean carbonate system for the purpose of removing CO 2 from the atmosphere, highlighting ecosystem-linked alkalinity production associated with coastal restoration as a comparatively underexplored pathway for renewed near-term focus. We argue that key challenges to large-scale deployment of these pathways include accurate quantification of carbon removal in monitoring, reporting, and verification protocols; the development and validation of models for carbon accounting; understanding broader environmental impacts; evaluating life-cycle resource and energy requirements; and establishing appropriate governance frameworks. Addressing these cross-cutting knowledge gaps will be critical for realizing the potential contribution of ocean carbonate system modification to climate mitigation.