NEW YORK (VINnews) — The world’s oceans are warming at an alarming rate, with rising sea levels, increasing acidity and widespread damage to marine ecosystems showing that the oceans are undergoing profound long-term changes, according to a major new report by more than 100 international scientists.

The 10th edition of the Copernicus Ocean State Report, released Wednesday, draws on more than four decades of observations from satellites, buoys and other sensors. Scientists warn that the changes already underway are occurring faster than many societies are prepared to handle.

The oceans absorb roughly 90% of the excess heat trapped in the Earth’s climate system by human greenhouse-gas emissions. In 2025 alone, they absorbed an estimated 23 zettajoules of additional heat, equivalent to the energy of about 12 Hiroshima-sized atomic bombs every second throughout the year. The 2025 increase marked the ninth consecutive year in which global ocean heat content reached a record high.

“The ocean is transforming before our eyes: warming, rising seas and ecosystem degradation are interconnected signs of significant and long-term change,” said Pierre Bahurel, director-general of Mercator Ocean International, which produces the report through the European Union’s Copernicus Marine Service.

The consequences are already being seen around the world. Global sea levels rose by about 3.8 millimeters per year between 1999 and 2025, but the rate increased to approximately 4.2 millimeters per year between 2012 and 2025. Rising temperatures contribute to this through both the expansion of warmer seawater and the melting of glaciers and ice sheets.

The ocean is also becoming more acidic. Its acidity increased by about 17% between 1985 and 2025, threatening organisms such as corals and shell-forming marine animals whose skeletons and shells become more difficult to build and maintain under increasingly acidic conditions.

Marine heatwaves are another growing concern. The Mediterranean and Black seas experienced exceptionally intense heatwaves, with temperatures in some areas more than 4.6 degrees Celsius above normal in 2024. Scientists say such prolonged warming can disrupt marine ecosystems, fisheries and the distribution of species.

The impact on coral reefs has also become increasingly severe. A separate component of the 2026 ocean assessment found that 84.4% of the world’s coral reefs experienced heat stress severe enough to cause bleaching between January 2023 and September 2025. Coral reefs support at least a quarter of marine species and provide food, coastal protection and livelihoods for hundreds of millions of people.

The polar regions are showing some of the clearest consequences. Arctic sea ice declined by roughly 490,000 square kilometers per decade between 1979 and 2025—an area approximately the size of Spain. In Antarctica, exceptionally low sea-ice levels have already affected wildlife. In 2022, four of five monitored emperor penguin colonies experienced total breeding failure after sea ice broke up before chicks were able to survive independently.

The Mediterranean is also experiencing sustained warming. Research included in the Copernicus report found that the Mediterranean has warmed by about 0.32°C per decade, contributing to increasingly frequent marine heatwaves.

Karina von Schuckmann, one of the report’s leading scientists, warned that the changes are particularly serious for island nations and coastal communities.

“For island states, ocean change is not a distant environmental issue; it is an immediate economic, development and security challenge,” she said.

The scientists emphasize that the findings are not based on isolated weather events but on long-term measurements showing broad changes across the global ocean. They say continued monitoring and improved forecasting will be essential for governments and coastal communities trying to prepare for rising seas, extreme marine heat, ecosystem disruption and other consequences of a rapidly changing ocean.