UK coastal waters are in the grip of an extreme marine heatwave, with sea surface temperatures soaring up to 5°C above the long-term average in some areas, according to the Met Office. This comes as global ocean temperatures have set new records for the 14th month in a row, intensifying concerns about the accelerating climate crisis.
Record-Breaking Sea Temperatures
The Met Office reported that waters around the UK, particularly in the North Sea and English Channel, have exceeded the threshold for a marine heatwave since early June. In some locations, temperatures have reached levels not seen since records began in the 1850s. The warmest anomalies are concentrated off the coast of Norfolk and into the southern North Sea, where temperatures are 4-5°C above normal.
Globally, the average sea surface temperature for June was 0.7°C above the 1991-2020 average, beating the previous record set in 2023. This marks the 14th consecutive month of record-high global ocean temperatures, a trend that scientists attribute primarily to human-induced climate change, exacerbated by the El Niño phenomenon.
Impacts on Marine Life and Weather
The extreme heat in UK waters is already having observable effects. Marine species such as jellyfish, sea bass, and even warm-water fish like red mullet are appearing in greater numbers. Conversely, cold-water species like cod are struggling, with potential long-term implications for fisheries. The heatwave also fuels more intense and frequent storms, as warmer seas provide more energy for weather systems.
Dr. Michaela Hegglin, a climate scientist at the University of Reading, said: "The fact that we are seeing such extreme temperatures in UK waters is a stark warning. The ocean has absorbed about 90% of the excess heat from global warming, and these records are a clear sign that the system is under immense stress."
Global Context and Future Projections
The UK marine heatwave is part of a global pattern. In the Atlantic, sea surface temperatures have been at record levels for over a year, contributing to the most active hurricane season on record in 2024. The Pacific Ocean, too, has seen prolonged warmth, disrupting marine ecosystems from the Great Barrier Reef to the Galapagos Islands.
Scientists warn that without drastic reductions in greenhouse gas emissions, marine heatwaves will become more frequent and severe. A study published in Nature Climate Change estimates that by 2050, such events could occur every year in many parts of the world, including UK waters.
For now, the UK's marine heatwave is expected to persist for at least another week, with temperatures remaining well above average. The Met Office advises that while sea temperatures may feel pleasant for swimmers, the underlying cause is a cause for serious concern.
