Model-based assessment of carbon dioxide removal effect through different ocean alkalinity enhancement technologies

This study investigates the long-term impacts of Ocean Alkalinity Enhancement (OAE) on global carbon cycling and climate systems under the high-emission SSP5-8.5 scenario using the UVic Earth System Climate Model (UVic_ESCM). By comparing three OAE technologies, namely, Hydroxide Ocean Liming (HOL), Limestone CO2 Leaching (LCL), and Olivine Ocean Dumping (OOD), key findings reveal distinct performance patterns. HOL achieves the most pronounced atmospheric CO2 reduction, lowering concentrations by -484.1 ppm by 2099, followed by OOD (-449 ppm), while LCL exhibits weaker net mitigation (-242.3 ppm) due to carbon release from mineral dissolution. In terms of oceanic carbon sequestration, LCL yields the highest cumulative increase owing to additional dissolved inorganic carbon (DIC) from carbonate dissolution. The study also identifies terrestrial carbon loss (-126 Gt C for HOL) and oceanic carbon re-release, underscoring the need to balance sequestration efficiency, dynamic feedbacks, and ecological risks. OAE markedly elevates seawater pH and aragonite saturation states (ΔΩ up to 50), though LCL shows minimal pH enhancement due to DIC buffering. These results highlight OAE’s potential to enhance marine carbon sinks and mitigate acidification, yet practical implementation requires optimizing mineral dissolution kinetics and minimizing supply-chain carbon emissions. The findings emphasize the importance of difference OAE technologies’ effects on carbon removal.