Marine Heatwaves Becoming More Frequent in the North Sea

Ocean Science, 30 June 2026

The North Sea has warmed about twice as fast as the global average sea surface temperature over the past 40 years. In addition to this long-term warming, short periods of unusually high ocean temperatures – known as marine heatwaves – are becoming more frequent. Using satellite observations together with ocean models, this study found that between 1993 and 2023 marine heatwaves in the North Sea occurred more often and generally lasted longer. On average, marine heatwaves occurred about twice per year at any given location and lasted around 15 days, equivalent to roughly 26 marine heatwave days per year. The strongest warming occurred in summer and early autumn, with the most intense marine heatwaves reaching about 1.2°C above normal. The study found that marine heatwaves result from a combination of long-term ocean warming, seasonal ocean conditions, and short-term weather patterns. Because marine heatwaves can alter heat exchange between the ocean and atmosphere, they can also influence coastal air temperatures and precipitation, in addition to affecting marine ecosystems.

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