Every part of the ocean is now affected by climate change, biodiversity loss, and pollution, according to the ninth Copernicus Ocean State Report.
The assessment, compiled by more than 70 international experts, documents accelerating ocean changes with major consequences for ecosystems, food security, economies, and human lives.
Ocean warming accelerates to record levels
The ocean absorbs around 90% of the excess heat generated by human greenhouse gas emissions. Since the 1960s, warming has accelerated dramatically.
Global sea surface temperatures reached a new high of 21°C in spring 2024, setting an alarming benchmark. Even seemingly small changes in sea surface temperature can destabilize weather systems, fisheries, and marine habitats.
Record marine heatwaves impact ecosystems and economies
Marine heatwaves broke records in 2023 and 2024, surpassing earlier peaks recorded in 2015 and 2016. In parts of the Atlantic, waters remained in heatwave conditions for more than 300 days in 2023. Such prolonged warming threatens fish stocks, reduces food production, and destabilizes coastal economies reliant on marine resources.
Sea level rise threatens heritage and coastal communities
Global sea levels rose by 228 millimeters between 1901 and 2024, with the pace of rise accelerating in recent decades. This trend increases flooding and erosion risks for millions living along Europe’s coasts.
Cultural landmarks are also vulnerable, with many UNESCO World Heritage sites in low-lying regions expected to face inundation within centuries.
Biodiversity under pressure from warming and acidification
Marine ecosystems are being reshaped by warming seas and increasing acidification. Micronekton species, small organisms critical to the marine food chain, are shifting toward the poles.
Meanwhile, 75% of nations emitting over 10,000 tonnes of plastic annually are located near already stressed coral reefs. These overlapping pressures heighten extinction risks and disrupt fragile ecosystems.
Invasive species damage fisheries in the Mediterranean
The longest marine heatwave ever recorded in the Mediterranean struck in summer 2023, raising water temperatures by 4.3°C above normal. Warmer waters fueled invasive species outbreaks. In Italy’s Po Delta, Atlantic Blue Crabs devastated clam harvests, leading to collapses of up to 100%. In Sicily, Bearded Fireworms disrupted artisanal fisheries.
Sea ice hits new lows in the Arctic and Antarctic
Arctic sea ice registered four record lows between December 2024 and March 2025. In March alone, ice coverage was 1.2 million square kilometers below the seasonal average, an area more than four times the size of Poland.
The Antarctic also recorded its third consecutive year of low ice extent in 2024, following an all-time low in 2023. In February 2025, Antarctic ice cover was 0.6 million square kilometers below the average, roughly twice the size of Italy.
Science and monitoring offer critical tools
Experts emphasize that while the findings are concerning, reliable data provide tools for action. The Copernicus Marine Service, implemented by Mercator Ocean International for the European Commission, offers monitoring and forecasting capacity to support policy, conservation, and resilience strategies.
EU Commissioner Andrius Kubilius described the report as an essential contribution to Europe’s Ocean Pact, highlighting its role in guiding sustainable coexistence with marine ecosystems.
Pierre Bahurel, Director General of Mercator Ocean International, warned that the ocean is now within planetary boundaries but stressed that operational science can still guide global resilience efforts.
Starfish Barometer strengthens reporting
For the first time, the report integrates the Starfish Barometer, a new annual monitoring tool launched at UNOC3 on World Ocean Day 2025. The barometer complements Copernicus data by tracking progress against key ocean sustainability goals, reinforcing the report’s role as a trusted global reference.
A warning and a roadmap
The 2025 edition of the Copernicus Ocean State Report delivers a clear message: ocean changes are accelerating at an alarming pace, but understanding them provides a blueprint for action. With ecosystems under unprecedented stress, the combination of science, policy, and public awareness will be vital in restoring balance between humanity and the ocean.
