Arctic waters are warming eight times faster than the global ocean average. Sea ice is vanishing at a rate of one Spain per decade — and the Mediterranean just endured its worst marine heatwave on record.
The message, in the words of the man who runs Europe's ocean observatory, is very clear: the ocean is changing rapidly. The tenth annual Copernicus Ocean State Report, published Wednesday by the EU's Copernicus Marine Service, says some of the most dramatic effects of global warming are unfolding at the poles — which hold around a fifth of the planet's ocean surface.
The Arctic is warming at a pace that dwarfs the global average. The combined sea-surface and sea-ice temperature of the Arctic rose 4.2°C between 1982 and 2024 — roughly 1°C per decade — against just 0.12°C per decade for the global ocean. In the Kara Sea, north of Siberia, the climb has been steeper still: 6.7°C since 1982, or 1.68°C per decade.
And the ice is keeping score. Arctic sea ice has shrunk by nearly half a million square kilometres per decade since 1979 — the equivalent of losing an area the size of Spain every ten years. As the ice retreats, Arctic coastlines stand exposed to wind and waves, worsening erosion and raising the stakes for coastal communities and the infrastructure they depend on. "The Arctic sea ice has been declining since the early '80s, leaving around 60 percent of coastal infrastructure vulnerable to erosion and sea level rise," Karina von Schuckmann, the report's director, told a media briefing.
Meanwhile, the warming is no longer a polar exclusive. The Mediterranean and Black seas suffered record-breaking marine heatwaves in 2024, with temperatures more than 4.6°C above normal. Marine ecosystems are shifting; waters are growing more acidic. And at the other end of the planet, ice loss in Antarctica is now threatening penguin populations on the frozen continent.
Step back, and the ledger is stark. Drawing on data stretching to 1960, the report shows average sea level rising by about 4.2mm per year since 2012. "The message is very clear," said Pierre Bahurel, director general of Mercator Ocean International, which runs the Copernicus Marine Service. "The ocean is changing rapidly." The consequences — for marine life, coastlines and communities — are already arriving, one heatwave at a time.
