Assessing the Mitigation Potential and Ecological Impacts of Carbon Dioxide Removal Technologies on Ocean Ecosystems

Climate change poses a critical threat to global ecosystems and human well-being, necessitating innovative solutions for carbon dioxide (CO₂) mitigation. This study employs the UVic-ESCM, an Earth system model of intermediate complexity, to investigate the potential and possible side effects of two marine-based CO₂ removal techniques, namely ocean alkalinity enhancement and macroalgae farming and sinking. Additionally, simulations from Bern3D-LPX for ocean alkalinity enhancement provide a model comparison.

Focusing on not only warming but also acidification and deoxygenation, the research aims to compare the theoretical deployment of these techniques in an emission-driven overshoot scenario (SSP5-3.4).To encompass uncertainty due to model parameters, we analyzed a perturbed parameter ensemble constrained by observations. Preliminary findings indicate that both techniques show promise in mitigating atmospheric CO₂ concentrations, with variations in their effects on climate and oceanic conditions. Both techniques show small cooling potential despite the large-scale theoretical deployment. While they do not provide an alternative to emission reductions, they could be beneficial in combating other human-induced stressors in the marine ecosystem. Both techniques demonstrate a potential to counteract ocean acidification, but we find that macroalgae farming and sinking contributes to localized deoxygenation.

This study contributes to the ongoing discourse on so-called ‘nature-based’ solutions for climate change mitigation by offering a nuanced evaluation of the theoretical upper potential in multiple mitigation dimensions as well as side effects of ocean alkalinity enhancement and macroalgae farming and sinking. The outcomes aim to inform future research directions and decision-making processes towards the development of effective and ecologically sustainable carbon dioxide removal strategies.