The ocean absorbs around 25% of annual anthropogenic CO₂ emissions, helping to slow global warming. However, this uptake alters ocean chemistry, increasing acidity and reducing the availability of carbonate ions essential for many marine organisms. As a result, ocean acidification poses growing risks to marine ecosystems, biodiversity, and the communities that depend on ocean resources.

OA’s impacts are already being observed in vulnerable regions, affecting marine species, ecosystem functioning, and coastal economies. Recent assessments suggest that the planetary boundary for ocean acidification has been exceeded, indicating increasing ecological and societal risks across large areas of the global ocean.

Although OA research has traditionally focused on global and open-ocean assessments, coastal and shelf seas remain insufficiently understood despite being among the regions most exposed to acidification and other stressors. These areas are also where most human-ocean interactions occur, making locally relevant knowledge essential for effective decision-making.

SAFESEA aims to bridge this gap by providing science-based, stakeholder-driven knowledge, tools, and indicators to support resilience and informed decision-making on OA in a multi-stressor context.

The project has six main objectives:

1. Produce scientific evidence through co-designed processes with stakeholders.
2. Address monitoring gaps across the surface and interior ocean, coastal zones, and polar regions.
3. Identify biological thresholds under the combined effects of OA, warming, deoxygenation, and other stressors.
4. Improve the accuracy and resolution of OA models and projections.
5. Integrate OA into governance frameworks, including considerations of justice and equity.
6. Promote communication, exploitation of results, and capacity building to ensure broad uptake and impact.

Through these activities, SAFESEA will strengthen monitoring, modelling, risk assessment, and governance approaches.

CMCC role
In SAFESEA, CMCC leads WP4, which focuses on improving the modelling and prediction of ocean acidification. The goal is to combine observations, advanced modelling techniques, data assimilation, and artificial intelligence to better understand how ocean acidification is evolving and how it may affect different marine regions in the future.

Activities
SAFESEA addresses key gaps in understanding and monitoring ocean carbon uptake and ocean acidification. Significant uncertainties remain regarding the magnitude and future evolution of the ocean carbon sink, while many regions of the ocean, particularly polar areas, the ocean interior, and Eastern Boundary Upwelling Systems, remain poorly observed.

To advance the state of the art, SAFESEA will expand and strengthen ocean acidification observations by generating new CO₂ flux measurements in the Southern Ocean and extending long-term monitoring time series in the Mediterranean Sea, Eastern Boundary Upwelling Systems, and the sub-polar Arctic. The project will improve OA assessments through comprehensive uncertainty analyses and by integrating new and existing datasets from both open-ocean and coastal environments.

SAFESEA will also investigate the environmental drivers of OA across different marine systems, disentangling the combined effects of warming, eutrophication, deoxygenation, nutrient dynamics, and biological processes. Particular attention will be given to coastal regions, where acidification can progress faster and where ecosystems are often exposed to multiple stressors simultaneously.

A major innovation of the project is the development of a UNESCO-IOC-aligned federated OA data system based on FAIR and CARE principles. This system will improve data interoperability, machine-readable metadata, and links with global observing systems and international policy frameworks, facilitating broader access and use of OA information.

In addition, SAFESEA will conduct targeted aerosol and trace metal measurements in remote regions to better understand their influence on ocean acidity and nutrient supply. Through these activities, the project will provide improved observations, integrated datasets, and advanced scientific knowledge to support more accurate assessments of ocean acidification and its impacts.

Expected results
SAFESEA will deliver major advances in the understanding, monitoring, forecasting, and governance of ocean acidification. The project will improve the representation of carbonate chemistry in coastal and shelf-sea environments through the development of a computationally efficient chemistry model integrated into high-resolution ocean models. It will also assess different downscaling approaches to support more reliable regional OA projections.

A key outcome will be the creation of a novel reanalysis product that integrates heterogeneous observations into a seamless global-to-coastal system, improving connectivity across scales and enhancing the use of observations in modelling frameworks. SAFESEA will also improve the representation of OA-sensitive biological processes by updating calcification algorithms and applying them within models and satellite-based assessments.

The project will advance forecasting capabilities by improving subseasonal-to-decadal OA predictions, identifying prediction skill windows for early warning systems, and assessing the reversibility of ocean acidification under climate overshoot and marine CO₂ removal scenarios.

SAFESEA will generate knowledge on biological responses to OA by developing performance curves for key species, conducting realistic multi-driver experiments, and scaling results from individual organisms to communities and biodiversity levels. It will also develop innovative indicators linking chemical and biological observations, providing improved tools for risk assessment and ecosystem monitoring.

SAFESEA will also support the integration of OA into decision-making and governance by co-designing future narratives and adaptation pathways with affected communities and providing evidence-based information to support adaptation and mitigation strategies. Through these activities, SAFESEA will deliver practical tools, improved projections, and policy-relevant knowledge for regional, European, and global stakeholders.

Partners

1. Norsk institutt for vannforskning (NIVA) STI
2. Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC)
3. Institut de recherche pour le développement (IRD)
4. Goeteborgs universitet
5. NORCE Research AS
6. Sorbonne Université
7. Centre national de la recherche scientifique (CNRS)
8. Kobenhavns universitet
9. Aarhus universitet
10. University of East Anglia (UEA)
11. University College London (UCL)
12. International Atomic Energy Agency (IAEA)
13. Potsdam-Institut für Klimafolgenforschung e.V. (PIK)
14. OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic