The ocean plays a vital role in regulating climate, supporting marine life, and providing food and jobs for billions of people. However, researchers warn that marine heatwaves are intensifying due to climate change, threatening the loss of these critical functions.
Similar to heatwaves on land, a marine heatwave is defined as a period of unusually high ocean temperatures, with extended duration and intensity. A groundbreaking new study, led by Dr Katie Smith at the Marine Biological Association, revealed the summers of 2023 and 2024 experienced nearly 3.5 times as many marine heatwave days compared to any previous year on record.
Results from this new study found nearly 10% of the global ocean hit record-high temperatures during 2023-24. The sustained spike in ocean temperatures cost lives and caused billions of dollars in storm damage, increased whale and dolphin stranding risks, harmed commercial fishing and sparked a global coral bleaching.
In Europe, marine heatwaves have contributed to record-breaking land temperatures across the British Isles, harming fish populations, and nearly causing the extinction of the fan mussel in the Mediterranean. Seabird populations in Scotland suffered as their food sources declined, while aquaculture industries faced losses due to harmful algal blooms. Warmer ocean temperatures have driven species to migrate northward, increasing wildlife-watching tourism around the British Isles. The same elevated temperatures also fuelled Storm Daniel, which brought catastrophic flooding to Greece, Bulgaria, and Turkey.
Good forecasting and prompt action have helped reduce the impact of marine heatwaves in several regions. Successful mitigation actions included moving corals and conches in Florida to deeper, cooler water and keeping endangered Tasmanian red handfish in aquariums until they could be returned to the wild. However, forecasting marine heatwaves has become more challenging since the Trump administration has fired hundreds of workers at the National Oceanic and Atmospheric Administration (Noaa), the US’s pre-eminent climate research agency housed within the Department of Commerce.
Ultimately the study emphasised that the more frequently marine heatwaves occur, the more difficult it is for affected areas to recover. The Marine Biological Association warns that if current levels of fossil fuel consumption and deforestation continue, marine heatwaves could become 20 to 50 times more frequent and up to 10 times more intense by the end of the century. To protect ocean ecosystems and coastal communities, transitioning from oil, coal and gas to renewable energy is the most urgent action we can take.