The landscape of science that addresses marine carbon dioxide removal (mCDR) and ocean alkalinity enhancement (OAE) has expanded rapidly. The IPCC 6th Report concluded that emissions reductions would need to be supplemented by CDR to reduce atmospheric CO₂ and limit global warming to well below 2 °C. The realization that negative emissions technologies are required to meet global warming mitigation goals has co-occurred with the growing risk of Ocean Acidification (OA), spawning approaches to artificially increase the alkalinity of the oceans. There are however many challenges of adding minerals to the ocean. In this work, we propose a property, namely the Takahashi factor (TF), to measure the potential of sea surface CO₂ decrease with 1% ocean alkalinity enhancement in the global ocean and, then, by coupling it to the Revelle factor (RF), we estimate the potential of mCDR after OAE. With this conceptual model, we show that the polar and subpolar ocean, as well as some mid-high latitude coastal seas, are most effective in OAE-based sea surface CO₂ reduction and uptake of anthropogenic CO₂ from the atmosphere while the subtropical gyres and some low latitude marginal seas are least effective in sea surface CO₂ reduction and CO₂ removal. Then, using a global ocean carbon model (MOM6), we further validate the prediction made by the simple conceptual model and discuss the impacts of ocean circulation and mixing as well as air-sea gas exchange on achieving the mCDR potential via OAE in the global ocean.
 

marine carbon dioxide removal (mCDR), ocean alkalinity enhancement (OAE), ocean CO2