Global warming has exceeded 1.5°C as a result of anthropogenic fossil fuel emissions, making it clear that deep emission reductions will need to be complemented by large-scale Carbon Dioxide Removal (CDR) to meet the Paris Agreement targets. The ocean plays a central role in the global carbon cycle, storing more than 97% of the world’s dissolved inorganic carbon and having absorbed approximately 20–30% of anthropogenic CO₂ emissions over recent decades. Despite the importance of these processes, marine (m)CDR techniques remain less developed than terrestrial approaches. Among technology-based marine CDR options, Ocean Alkalinity Enhancement (OAE) has attracted particular attention in scientific, technological, and policy debates. However, significant uncertainties remain regarding its effectiveness, techno-economic feasibility, environmental impacts, and governance implications. OAeSIS aims to address these key gaps by advancing understanding of the socio-economic, governance, and impact dimensions of OAE, thereby supporting informed decision-making and future climate policy development.

OAeSIS has been developed within the framework of the “Land, ocean and water for climate action” work programme and will be implemented in close alignment with related funded activities, in particular with its sister topic “Monitoring the global ocean for safe, verifiable, and sustainable marine carbon dioxide removal (mCDR)”.

General Objectives

OAeSIS adopts an integrated, interdisciplinary methodology structured around five research themes aligned with the project’s core objectives:

1. Identify the social, ethical and governance constraints on OAE deployment.
2. Improve understanding of the biogeochemical processes and interactions triggered by OAE deployment.
3. Quantify the scaling potential of OAE deployments and their climate change mitigation capacity.
4. Quantify the impacts of OAE on key calcifying species, communities and biodiversity.
5. Assess the feasibility and sustainability of OAE as a tool for counteracting climate change and ocean acidification

Expected Results

OAeSIS will generate knowledge and data to support robust assessments of Ocean Alkalinity Enhancement and to inform pathways toward implementation that are effective, sustainable, and just. This will be achieved through a step change in understanding biogeochemical responses to different OAE deployment options, their efficacy at scale, and potential impacts on marine biology and biodiversity; the strengthening of European observing and modelling infrastructures to monitor OAE across spatial and temporal scales; and the development of sustainable implementation pathways, governance frameworks, and engagement strategies aimed at ensuring fair and equitable deployment.

The project will contribute to key EU policy objectives, including:

• Achieving a climate-neutral Europe by 2050, as set out in the European Climate Law.
• Halting and reversing biodiversity loss, in line with the European Green Deal and the Kunming–Montreal Global Biodiversity Framework.
• Building a fair and inclusive Europe that protects citizens and expands opportunities, as outlined in the European Pillar of Social Rights Action Plan.

OAeSIS will also support broader global sustainability frameworks, including the UN Sustainable Development Goals, the Paris Agreement, and the Convention on Biological Diversity.