The 7th edition of the Copernicus Ocean State Report delivers a comprehensive scientific check-up on our global ocean, revealing a disturbing diagnosis of accelerating change driven by human activity.
Published September 2023
The ocean is the Earth's life-support system, regulating our climate, feeding billions, and providing half the oxygen we breathe. Yet this vital system is undergoing dramatic changes that threaten its very functioning. The 7th edition of the Copernicus Ocean State Report (OSR7) delivers a comprehensive scientific check-up on our global ocean, revealing a disturbing diagnosis of accelerating change driven by human activity.
From 30 institutions across 14 countries 4
Tracking changes across latitude, longitude, depth, and time 2
What emerges is a picture of an ocean in flux, with potentially grave consequences for ecosystems, weather patterns, and human communities worldwide.
The Copernicus Ocean State Report examines what scientists call the "Blue, Green, and White Ocean"—encompassing physics (currents, temperature), biogeochemistry (marine life, nutrients), and sea ice 2 . This comprehensive approach allows researchers to connect dots between different ocean processes and their collective impact on the Earth system.
| Parameter | Trend | Significance |
|---|---|---|
| Ocean Heat Content | Record high in 2022 | Contributes to sea level rise, impacts marine life |
| Marine Heatwaves | Increasing frequency & intensity | Causes ecosystem shifts, coral bleaching, fisheries disruption |
| Sea Surface Temperature | Reached 21.1°C in April 2023 | Exceeded previous 2016 record 6 |
| Sea Ice Extent | Record low around Antarctica | 2.2 million km² lost in June 2023 alone 6 |
| Ocean Circulation | Showing signs of weakening | Affects global heat distribution, weather patterns |
While global trends are concerning, some regions are experiencing even more dramatic changes. The Mediterranean Sea has emerged as a particularly vulnerable hotspot, warming 20% faster than the global average 6 . In August 2023, the Mediterranean's surface temperature reached a staggering 28.7°C, the highest median recording since at least 1982 6 .
This accelerated warming poses a grave threat to the Mediterranean's remarkable biodiversity. Home to more than 17,000 marine species 6 , this semi-enclosed sea faces potential ecosystem collapse as species struggle to adapt to rapidly changing conditions.
Mediterranean warming compared to global average 6
One of the innovative methodologies highlighted in OSR7 is the development of a new scientific method for monitoring coastal upwelling 1 . Coastal upwelling is a crucial process that brings cold, nutrient-rich waters from the deep ocean to the surface, supporting some of the world's most productive fisheries and ecosystems.
Understanding changes in these patterns is vital, as disruptions can affect water quality, fisheries, and aquaculture production in coastal areas 1 . Traditionally, monitoring upwelling has been challenging due to the complex interplay of factors that drive it and the localized nature of these events.
| Tool/Technique | Function | Application in OSR7 |
|---|---|---|
| Satellite Observations | Measure sea surface temperature, salinity, ocean color, waves | Global coverage of surface ocean properties 1 |
| In Situ Measurements | Direct measurements from buoys, research vessels | Ground-truthing satellite data, depth profiles 1 |
| Ocean Reanalysis | Combines models with observations using data assimilation | Creates comprehensive 4D view of ocean 1 |
| High-Frequency Radar (HFR) | Monitors coastal surface currents in real time | Coastal upwelling monitoring 1 |
| High-Performance Computing | Enables complex modeling and data integration | 4D ocean forecasts, trend analysis 5 |
The proof-of-concept testing confirmed that this new coastal upwelling index successfully captured the dynamics of upwelling events in the pilot areas 1 . The method proved robust enough for direct upwelling monitoring over any coastal area of the global ocean.
One dramatic example of extreme events affecting upwelling came from the Balearic Islands in November 2021, when an intense and long-lasting storm named "Blas" hit the area 1 . The storm resulted in intense upwelling along the northwestern coasts of Mallorca and Ibiza, causing coastal surface temperatures to become up to 6°C colder than usual 1 .
Among the most concerning findings in OSR7 relates to the weakening of crucial ocean circulation patterns. The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, plays a vital role in redistributing heat around our planet 6 . This circulation system acts as a global conveyor belt, transporting warm water from the tropics toward the poles and cold water back south.
The report highlights alarming evidence that the AMOC is showing signs of dramatic weakening and could potentially reach a tipping point by mid-century 4 . The mechanism behind this slowdown relates to the influx of freshwater from melting ice, particularly from Greenland and Antarctica.
Key Changes: Record low oxygen levels to 600m depth
Potential Impacts: Marine life stress, habitat compression 5
Key Changes: Freshwater content decreasing overall, but patterns vary by sub-basin
Potential Impacts: Ecosystem changes, altered circulation 1
Key Changes: 50-60% decrease in phytoplankton from heatwaves
Potential Impacts: Marine food web disruption 6
The report also sounds the alarm about decreasing oxygen levels in certain marine areas. In the southern Adriatic Sea, researchers observed a record low oxygen level extending to almost 600 meters below the surface 5 . This oxygen depletion, known as deoxygenation, poses a direct threat to marine life that depends on oxygen for survival.
The study of the Adriatic Sea highlighted the critical role of heat fluxes, ocean currents, and biological production in driving dissolved oxygen variations 1 . Researchers also identified a potential regime shift in regional circulation that could have substantial implications for ocean ventilation in the Ionian-Adriatic region 1 .
Record low oxygen levels in Southern Adriatic Sea 5
The 7th edition of the Copernicus Ocean State Report delivers an unambiguous message: our ocean is changing at an unprecedented pace, with consequences that extend far beyond marine ecosystems to touch every aspect of human life. From the fish on our plates to the weather patterns that determine crop yields, the ocean's changing state directly affects human societies.
Yet within this alarming assessment lies cause for measured hope. The detailed scientific knowledge contained in OSR7 provides the foundation for informed action. As the report emphasizes, protecting and preserving the ocean is essential for ensuring a sustainable future, maintaining biodiversity, regulating climate, supporting economies, and safeguarding human health and well-being 1 .
Adoption of the Treaty of the High Seas (BBNJ) at the United Nations 1
Publication of the 7th Copernicus Ocean State Report
Implementation of scientific findings into policy and conservation efforts
Ultimately, the Copernicus Ocean State Report serves as both warning and guide. By documenting the precise changes occurring in our ocean, it equips policymakers, industries, and citizens with the knowledge needed to make decisions that protect rather than harm our planetary life-support system. The ocean's future—and ours—depends on how we respond.