An analysis of ocean alkalinity enhancement models and their limitations
Date
2025
Auteurs
Martin, Katherine Rena
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Résumé
As atmospheric carbon dioxide (CO2) levels continue to rise, increasing attention is being given to exploring mitigation techniques that could potentially enhance the natural drawdown of CO2. One such mitigative intervention is ocean alkalinity enhancement (OAE), which has drawn the scientific community's attention over the past decade, as a natural form of carbon capture and a hopeful solution to the excess carbon dioxide in our atmosphere. OAE involves dissolving alkaline materials into ocean surface waters to increase its natural CO2 buffering capacity. Limestone and lime have received plenty of attention given their widespread availability. Here, the following paper will address the order one policy-relevant question of whether OAE represents a viable CO2 removal solution to global warming.
The UVic Earth System Climate Model (ESCM) was used to explore the potential of OAE interventions under representative concentration pathways (RCP) 2.6, 4.5, 6.0, and 8.5. For each RCP, three OAE interventions were implemented. First, it was assumed that the global annual production of limestone was crushed, uniformly distributed across the surface waters of the global ocean, where it immediately dissociates in the surface water. Second, it was assumed that the global production of limestone was converted to lime, with the CO2 released in this process being added to the atmosphere. In the third intervention, the second intervention was repeated, though sequestering the CO2 arising from lime production. Although lime and limestone OAE have been put forward as major solutions for carbon dioxide emissions, the results show that despite slightly raising pH, lowering CO2 concentrations and lowering air surface temperatures, the change is small, suggesting that OAE interventions have little potential for mitigating global warming.
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ocean alkalinity enhancement, climate mitigation, negative emissions