The UK's ocean temperatures are hitting unprecedented levels as an "extreme" marine heatwave grips the country. With much of Europe still reeling from its most severe heatwave on record last month, scientists warn that persistently high sea temperatures could have devastating consequences for marine life.
According to Dr Ségolène Berthou, an air-sea interaction specialist at the Met Office, the rapid development of these elevated temperatures is due in part to the ocean's inability to cool down between successive land-based heatwaves. This current event marks the third and most intense marine heatwave affecting the UK this year, with no immediate signs of abatement.
UK sea temperatures are approximately 2C warmer than typical for this time of year, with some localised areas experiencing even more extreme conditions – up to 4-5C above their usual levels. The implications are severe, particularly given that oceans absorb over 90% of the Earth's excess energy, largely driven by fossil fuel combustion.
Globally, sea surface temperatures have broken previous records for this time of year, a development confirmed by both the Copernicus Climate Change Service and the Copernicus Marine Service. This was somewhat anticipated due to the onset of El Niño conditions, predicted to be among the strongest in decades. UN Secretary-General António Guterres has urged world leaders to treat the arrival of El Niño as an "urgent climate warning," advocating for decisive action to transition away from fossil fuels.
Marine scientists warn that these extreme conditions could trigger "mass-mortality events" for vulnerable species, while prolonged periods of unusually warm water may alter the distribution of commercially important fish and shellfish. Professor John Pinnegar, principal scientist at the Centre for Environment, Fisheries and Aquaculture Science, highlights the potential disruption to existing ecosystems and the introduction of new species to UK waters.