Key facts
- The UK is experiencing an 'extreme' marine heatwave with sea temperatures potentially 4-5C above average.
- The event is linked to recent heat domes and long-term ocean warming driven by climate change.
- Marine life faces significant stress, potential mass mortality, and shifts in species distribution.
- Warm-water species like octopus are increasing in UK waters, impacting native species and fisheries.
- Scientists warn that without greenhouse gas emission reductions, such events will become more frequent.
The UK is currently experiencing an "extreme" marine heatwave, with sea temperatures potentially reaching 4-5C above average in some areas, according to the Met Office. This phenomenon is attributed to the rapid development of atmospheric conditions driven by recent heat domes, which prevented oceans from cooling sufficiently between land-based heatwaves. Oceans absorb over 90% of excess energy in the Earth's system, largely due to fossil fuel burning.
This marks the third and most intense marine heatwave of the summer for the UK, with average temperatures already 2C warmer than usual. Globally, sea surface temperatures have broken records, anticipated to follow strong El Niño conditions. UN Secretary-General António Guterres has urged immediate climate action, emphasizing the need to end fossil fuel reliance and transition to renewables.
Scientists warn these extreme conditions can lead to "mass-mortality events" for marine species and alter the distribution of commercially important fish. For instance, record numbers of octopuses have appeared off the south-west coast of England, impacting native species and fisheries. The southern North Sea and English Channel, being shallow, heat up quickly, making them susceptible to intense and prolonged heatwaves. Without significant reductions in greenhouse gas emissions, such marine heatwave conditions are projected to become the norm by mid-to-late century.