The Met Office says a marine heatwave could reach "extreme" levels around parts of the UK later this week, with sea temperatures in places 4 to 5C above average and the strongest warmth off eastern and southern England. Long periods of elevated sea heat can trigger mass die-offs of seagrasses, kelp forests and shellfish and encourage greater numbers of warm-water species such as octopus. Scientists say this event has been fuelled by the "heat domes" that produced record air temperatures in May and June, on top of long-term ocean warming from climate change. Shallow areas such as the southern North Sea and the English Channel heat up quickly, raising fears the episode could be particularly intense and long-lasting for those regions. Researchers have already documented longer-term shifts, with cool-adapted species such as cod moving north while some warm-water species have increased around south-west England, and scientists warn those changes can bring declines in key fish and displacement or disease risks. "We are starting to see temperatures now that we would expect to see at the height of summer, [at the] end of August," said Dr Zoe Jacobs of the National Oceanography Centre, and Dr Ségolène Berthou of the Met Office warned marine heatwave conditions are likely to become average by the middle-to-end of the century if greenhouse gas emissions are not cut.
