An unprecedented marine heatwave off the coasts of the UK and Ireland is posing a significant threat to marine species, with sea temperatures several degrees above normal, breaking records for late spring and early summer. The Guardian reports: The Met Office said global sea surface temperatures in April and May reached an all-time high for those months, according to records dating to 1850, with June also on course to hit record heat levels. The US National Oceanic and Atmospheric Administration has categorized parts of the North Sea as being in a category four marine heatwave, which is considered “extreme,” with areas off the coast of England up to 5C above what is usual. The Met Office says temperatures are likely to remain high because of the emerging El Nino weather phenomenon.
Daniela Schmidt, a professor of earth sciences at the University of Bristol, said: “The extreme and unprecedented temperatures show the power of the combination of human-induced warming and natural climate variability like El Nino. While marine heatwaves are found in warmer seas like the Mediterranean, such anomalous temperatures in this part of the north Atlantic are unheard of. They have been linked to less dust from the Sahara but also the North Atlantic climate variability, which will need further understanding to unravel. Heat, like on land, stresses marine organisms. In other parts of the world, we have seen several mass mortalities of marine plants and animals caused by ocean heatwave which have caused hundreds of millions of pounds of losses, in fisheries income, carbon storage, cultural values and habitat loss. As long as we are not dramatically cutting emissions, these heatwaves will continue to destroy our ecosystems. But as this is happening below the surface of the ocean, it will go unnoticed.”
Dr Dan Smale from the Marine Biological Association has been working on marine heatwaves for more than a decade and was surprised by the temperatures. He said: “I always thought they would never be ecologically impactful in the cool waters around UK and Ireland but this is unprecedented and possibly devastating. Current temperatures are way too high but not yet lethal for majority of species, although stressful for many … If it carries on through summer we could see mass mortality of kelp, seagrass, fish and oysters.”
Piers Forster, a professor of climate physics at the University of Leeds, said: “Both Met Office and NOAA analyses of sea-surface temperature show temperatures are at their highest ever level — and the average sea-surface temperature breached 21C for the first time in April. These high temperatures are mainly driven by unprecedented high rates of human-induced warming. Cleaning up sulphur from marine shipping fuels is probably adding to the greenhouse gas driven warming. The shift towards El Nino conditions is also adding to the heat. There is also evidence that there is less Saharan dust over the ocean this year. This normally reflects heat away from the ocean. So in all, oceans are being hit by a quadruple whammy — it’s a sign of things to come.”
