The UK is bracing for its third heatwave of the year, with temperatures forecast to reach 34-35C in parts of southern England, while scientists warn that an extreme marine heatwave could trigger mass die-offs of sea life off the coasts. The marine heatwave, currently strongest off the coasts of eastern and southern England, could see sea temperatures 4-5C above average in places, according to the Met Office. Long periods of sea heat can trigger mass die-offs among seagrasses, shellfish and other species, and encourage greater numbers of warm-water creatures including octopus.
The marine heatwave has been fuelled by the "heat domes" that brought record-breaking air temperatures in May and June, on top of long-term ocean warming due to climate change. Important marine habitats such as seagrasses and kelp forests are suited to cooler waters and can experience high levels of heat stress when temperatures surge, reducing growth or even leading to mass mortality events, which could have knock-on effects for species that rely on these habitats.
“Extreme marine heatwave threatens UK sea life as third heatwave brings temperatures up to 35C.”
"We're 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 in Southampton. "So, if this event keeps coming… we might start seeing some serious impacts on ecological systems." Researchers have also noticed longer-term shifts in UK marine life: cool-adapted species such as cod are moving further north, while numbers of some warm-water species such as octopus have risen around south-west England.
"It can be exciting to see new species arrive… but the problem is we've also got the negative impacts of that," said Prof Matt Frost of the Plymouth Marine Laboratory. "We're seeing a decline in the numbers of cod and other key species… you're also getting other species that could displace native species. That could bring disease [and] all sorts of problems." Increasing numbers of octopus may offer a new market for fishermen, but can hit populations of crabs, lobster, scallops and other shellfish on which they prey.
This third heatwave, described by Met Office Deputy Chief Forecaster Steven Keates as the third such event in the UK this year, is not expected to be record-breaking: "Unlike the May and June heatwaves, we are not expecting this heatwave to be record-breaking." Nevertheless, the warm conditions mean individuals need to take safety precautions. For motorists, Mike Fazal, motoring expert and CEO of Leasing.com, advises the "45mph air-con rule": below that speed, opening windows is more fuel-efficient, but above 45mph, air conditioning is better because open windows create aerodynamic drag that makes the engine work harder. Studies indicate that air conditioning can raise fuel consumption by about 10%, while driving with windows open at higher speeds can push fuel use up by as much as 20%.
