IOC leads efforts to close key knowledge gaps in understanding the ocean carbon sink to support stronger climate action

A global scientific foundation for better climate decisions

The Integrated Ocean Carbon Research (IOC-R) Report , developed by 72 authors and 13 reviewers from 23 countries, offers the most comprehensive evaluation to date of the processes driving ocean carbon uptake and storage, and identifies the research priorities required to strengthen global climate planning.

A critical knowledge gap

Despite major scientific advances, significant uncertainties remain in estimating how much carbon the ocean absorbs each year. Current models diverge by 10-20% globally, and even more in certain regions. These discrepancies stem from limited observations and incomplete understanding of how physical, biological, chemical, and human-driven processes shape the ocean carbon cycle.

Among the most influential knowledge gaps are:

• Warming, stratification, and changes in ocean mixing

• Shifts in plankton communities, microbial activity, and food-web dynamics

• Carbon transfers across coastal, land-ocean, and polar interfaces

• Growing impacts of industrial activities, including trawling, dredging, drilling, aquaculture, and deep-sea mining

• Uncertainties around future marine carbon dioxide removal (mCDR) approaches, such as seaweed cultivation, iron fertilization, and alkalinity enhancement

Together, these unknowns mean governments are making climate decisions without fully understanding how the ocean, our largest carbon sink, will behave in the future.

Why this matters for societies worldwide

If the ocean absorbs less carbon in the coming decades, more CO₂ will remain in the atmosphere, intensifying warming and increasing risks for communities, ecosystems, and economies. This uncertainty directly affects:

• National climate strategies and emissions targets

• Projections used in IPCC assessments

• Coastal communities facing sea-level rise, warming waters, and extreme events

• Decisions on carbon removal, adaptation pathways, and long-term planning
  

As IOC-R co-chair Professor Carol Robinson emphasized during the report launch:

"The ocean has been our greatest climate ally. But we still do not fully understand how much longer it can keep absorbing carbon at today's rates."

Five priority areas where the world must act now

The IOC-R Report identifies five scientific focus areas where knowledge gaps are most urgent and where coordinated global research is essential:

1. Evolution of the ocean carbon sink in a changing climate

Uncertainties in air-sea fluxes, riverine inputs, ice-driven processes, warming, stratification, and extreme events limit accurate projections.

2. The changing role of ocean biology

Plankton communities, microbial processes, particle sinking, and remineralization regulate long-term carbon storage, yet these biological processes remain poorly understood.

3. Carbon exchanges across the land-ocean-ice continuum

Coastal zones, estuaries, river plumes, permafrost regions, and polar systems are hotspots of carbon transfer but remain severely under-measured.

4. Impacts of industrial activities on the carbon cycle

Trawling, dredging, drilling, aquaculture, deep-sea mining, and plastic pollution disrupt sediments, alter ecosystems, and reshape food webs, influencing carbon pathways in ways not yet fully quantified.

5. Future changes by ocean-based climate interventions (mCDR)

Approaches such as seaweed cultivation, artificial upwelling, alkalinity enhancement, or iron fertilization present unknown risks for ecosystems and carbon permanence, and require rigorous monitoring frameworks.

Key steps to close the knowledge gaps

The report highlights four essential steps to reduce uncertainties and better align global climate action with the ocean's evolving role:

• Integrate global observing efforts across satellites, autonomous platforms, and sustained in-situ measurements.

• Refine models to better capture physical, chemical, and biological processes.

• Strengthen scientific capacity worldwide, particularly in data-limited regions.

• Foster cross-disciplinary research to connect scientific insight with societal needs.
  

A turning point for ocean-climate service

The IOC-R Report marks an important milestone in understanding the ocean's role in climate regulation. As the impacts of climate change accelerate, strengthening our scientific foundations is not optional, it is essential.

The message is clear: closing the world's ocean-carbon knowledge gaps is vital to support stronger, more effective climate action.