Katherine Martin

Topic

An Analysis of Ocean Alkalinity Enhancement Models and Their Limitations

School of Earth and Ocean Sciences

Date & location

• Monday, September 8, 2025
• 1:00 P.M.
• Bob Wright Centre, Room A319

Examining Committee

Supervisory Committee

• Dr. Andrew Weaver, School of Earth and Ocean Sciences, University of Victoria (Co-Supervisor)
• Prof. Michael Eby, School of Earth and Ocean Sciences, UVic (Co-Supervisor)
• Dr. Roberta Hamme, School of Earth and Ocean Sciences, UVic (Member)

External Examiner

• Dr. Shannon Fargey, Department of Geography, UVic

Chair of Oral Examination

• Dr. Sarah Nutter, Counselling Psychology, Faculty of Health, UVic

Abstract

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 is addressed.

The UVic Earth System Climate Model was used to explore the potential of OAE interventions under representative concentration pathways (RCPs) 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 and uniformly distributed across the surface waters of the global ocean, it is further assumed that the crushed limestone 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.