‘Extreme’ Marine Heatwave Forecast for Parts of UK Waters

Parts of the UK’s coastal waters could experience an “extreme” marine heatwave later this week, according to the Met Office, raising concerns about the potential impact on marine ecosystems.

The unusually warm conditions are currently most pronounced off the east and south coasts of England, where sea surface temperatures are expected to reach 4–5°C above average in some areas.

Scientists say the marine heatwave has developed following the prolonged periods of exceptionally warm weather experienced during May and June. The persistent high-pressure systems, often referred to as “heat domes”, allowed air temperatures to soar before transferring that heat into surrounding seas. This has been compounded by the long-term warming of the world’s oceans driven by climate change.

Marine heatwaves are prolonged periods of unusually high sea surface temperatures. While they have occurred in UK waters before, researchers believe this event could be particularly intense and long-lasting, especially across parts of the English Channel and the southern North Sea.

The rise in sea temperatures poses a significant threat to marine habitats including seagrass meadows and kelp forests, both of which are adapted to cooler conditions. Extended periods of elevated temperatures can reduce growth, cause widespread die-offs, and affect the many species that rely on these important underwater ecosystems.

Scientists have also observed longer-term changes in the distribution of marine life around the UK. Species that favour cooler waters, such as cod, are gradually moving further north, while warmer-water species, including octopus, are becoming increasingly common in south-west England.

Although natural environmental cycles and fishing pressure also influence marine populations, warming seas are considered a major factor behind these changes.

The increase in octopus numbers may create new opportunities for commercial fisheries, but it could also place additional pressure on shellfish populations such as crabs, lobsters and scallops, which form an important part of the octopus diet.

The English Channel and southern North Sea are particularly susceptible to rapid warming because of their relatively shallow depths. With UK seas having warmed steadily since the 1980s, scientists warn that marine heatwaves are becoming increasingly likely and are expected to become more frequent and intense unless greenhouse gas emissions are significantly reduced.