Context
Climate change is increasing the likelihood of abrupt and non-linear changes in the ocean, while also intensifying extreme events such as marine heatwaves. Processes such as a potential collapse of the Atlantic Meridional Overturning Circulation (AMOC), a slowdown of the North Atlantic Subpolar Gyre, or persistent extreme ocean temperatures could trigger cascading effects on marine ecosystems, ecosystem services and the societies that depend on them.
Understanding these processes is particularly complex because responses occur across different spatial and temporal scales and can propagate from the ocean’s physical and chemical system to ecosystems and, ultimately, to social and economic systems.
OceanNexus addresses this challenge through an integrated approach that links climate, ecological and social modelling to improve our understanding and prediction of these changes and their consequences. The project will analyse five European regions with distinct characteristics: the North Atlantic, the Baltic Sea, the Bay of Biscay, the north-western Mediterranean and the Ebro Delta shelf.
Objectives
The main objective of OceanNexus is to improve our understanding of, and ability to predict, short-, medium- and long-term changes in the ocean, marine ecosystems and their societal consequences under extreme climate variability, including potential tipping points.
To achieve this, the project aims to:
- Develop detailed projections of future ocean changes using advanced high-resolution Earth system models, with a particular focus on potential AMOC transitions, a slowdown of the Subpolar Gyre and persistent marine heatwaves.
- Improve the regionalisation of climate projections and analyse the role of ocean eddies in extreme events and tipping points.
- Develop new statistical tools to estimate the probability and impacts of critical changes in the AMOC under different emissions scenarios and establish safe operating spaces across different time horizons.
- Predict the combined response of climate, ecological and social systems across the five European case studies.
- Model marine ecosystems by combining different ecological models with climate scenarios and Essential Climate and Ocean Variables derived from existing observation programmes.
- Identify the conditions that may trigger critical transitions, abrupt changes or collapses in marine ecosystems, and quantify how these effects propagate from physical and chemical systems to ecological and social systems.
- Develop adaptive and precautionary management principles and tools to help policymakers, managers and planners address future regime shifts in marine socio-ecological systems.
AZTI’s role
AZTI will contribute to the project by studying tipping points in three systems in the Bay of Biscay linked to ocean warming:
Bifurcation in primary production: Ocean stratification driven by warming may cause a negative amplification of biomass across trophic levels through bottom-up control, reducing the ocean’s capacity to regulate the climate through the biological carbon pump. In the Bay of Biscay, observed trends and projections for primary production remain highly uncertain because of potential bifurcation pathways associated with stronger ocean stratification in spring, which would reduce primary production, or increased winter mixing, which would enhance it.
Tropicalisation of biodiversity: Identifying the underlying ecological processes that drive the reorganisation of marine species in a warming ocean — particularly increases in warm-water species and declines in cold-water species, i.e. tropicalisation — is crucial for climate change adaptation, as these processes may lead to abrupt declines in species richness beyond currently unknown thresholds.
Alternation in marine resources: Commercial fish species such as anchovy and sardine show alternating patterns of abundance in certain fishing grounds and undergo marked population fluctuations worldwide. The factors driving these strong fluctuations in the Bay of Biscay remain poorly understood and are of major relevance for the management of these stocks.
Expected results
OceanNexus will deliver an integrated framework for analysing how tipping points and extreme climate events can propagate through the connections between the ocean, marine ecosystems and society.
The project will develop high-resolution climate projections, marine ecosystem models, integrated risk assessments, and new statistical and artificial intelligence tools to identify early warning signals of critical changes in both the ocean and social systems.
The five case studies will enable comparisons of physical, ecological and social responses under different emissions scenarios and time horizons, as well as the identification of vulnerabilities, cascading risks and potential safe operating spaces.
OceanNexus will also provide decision-oriented indicators and contribute to improving the monitoring of Essential Climate Variables (ECVs) and Essential Ocean Variables (EOVs).
Expected impact
OceanNexus aims to contribute to the development of more resilient, adaptive and sustainable European ocean and coastal systems by transforming scientific knowledge on climate tipping points into useful information for planning and management.
The involvement of policymakers and other stakeholders through science-policy panels will support the co-design of adaptation strategies, governance models and precautionary management measures aimed at reducing vulnerabilities and protecting ecosystem services.
The results are intended to contribute to international scientific assessments and processes such as the IPCC, IPBES and the United Nations Framework Convention on Climate Change (UNFCCC), while also strengthening open science and social learning.
The project will also contribute to Sustainable Development Goals 13 (Climate Action) and 14 (Life Below Water), the EU Mission on Adaptation to Climate Change, the European Green Deal, the EU Strategy on Adaptation to Climate Change and the objectives of a sustainable blue economy.
