Copernicus ocean report details rapid Arctic warming and infrastructure risks

Global ocean heating and acidification

The European Union Copernicus Marine Service published its 10th annual Ocean State Report on 30 September 2026, compiling four decades of observations from satellites, buoys, and underwater sensors. The findings, coordinated by Mercator Ocean International with contributions from more than 100 international scientists, describe widespread thermal and ecological shifts throughout the world's oceans. Global waters absorb approximately 90% of the excess heat trapped in the atmosphere by greenhouse gas emissions, along with roughly one-third of human-generated carbon dioxide. Over the last 20 years, the global ocean warming rate doubled, with sea surface temperatures reaching peak levels in 2023, 2024, and 2026. In 2025, marine systems absorbed 23 zettajoules of additional heat, marking a ninth consecutive annual record and matching 40 times total global energy consumption for that year. Ocean acidity also rose 17% across four decades, impeding shell and skeleton formation for corals, mollusks, and crustaceans.

The ocean is transforming before our eyes: warming, sea level rise and ecosystem degradation are interconnected signs of significant and long-term changes.

Accelerated warming across polar seas

Polar oceans account for 20% of global marine surface area and experience the fastest rates of warming. Surface temperatures in the Arctic Ocean increased by 4.2°C between 1982 and 2024, representing a pace of roughly 1.0°C per decade compared to the global ocean mean of 0.12°C per decade. Specific sectors of the Arctic warmed even faster, with Russia's Kara Sea registering a surface temperature rise of 6.7°C over 40 years. This sustained thermal increase reduced Arctic sea ice extent by 17% over 42 years. On average, the Arctic ice pack shrinks by 490,000 square kilometres every decade, an area comparable to the total landmass of Spain.

Coastal infrastructure risks and polar wildlife

The loss of sea ice combines with the thawing of mainland permafrost to expose Arctic coastlines to wave activity and marine erosion. This dual degradation threatens northern settlements and industrial sites situated along the coast. In the Southern Ocean surrounding Antarctica, changing ice dynamics affect marine fauna dependent on stable platforms. A severe contraction of Antarctic sea ice in 2022 caused widespread breeding failures among sea birds, with uninsulated chicks drowning or freezing after ice broke apart prematurely. Scientists project that over 90% of emperor penguin colonies could face quasi-extinction by 2100 if sea-ice retreat continues at its current pace.

About 60% of Arctic coastal infrastructure is already vulnerable to erosion and sea level rise.

Sea level measurements and regional heatwaves

Global sea levels rose at an average rate of 3.8 millimetres per year since 1999, with the pace accelerating to 4.2 millimetres annually between 2012 and 2025. Regional basins in Europe experienced intense thermal stress, with the Mediterranean Sea warming at 0.32°C per decade. Extended marine heatwaves in both the Mediterranean and Black Seas penetrated into deep layers, with certain high-temperature anomalies persisting longer than one month. Western Mediterranean waters demonstrated a marked acceleration in sea-level rise, while changes in the eastern Mediterranean displayed wider geographic variation.