A groundbreaking new study published in Nature Climate Change, led by Dr Katie Smith, Postdoctoral Research Assistant at the Marine Biological Association (MBA), reveals that the summers of 2023 and 2024 experienced nearly 3.5 times as many marine heatwave days compared to any previous year on record. This surge, fuelled by climate change and exacerbated by El Niño, led to multiple record-breaking heatwaves and caused billions of dollars in damage globally.
The ocean plays a vital role in regulating climate, supporting marine life, and providing food and jobs for billions of people. However, researchers say that as marine heatwaves intensify due to climate change, these critical functions are at risk.
Over the past two years, marine heatwaves have led to widespread disruptions, including the closure of fisheries and aquaculture industries, increased strandings of whale and dolphins, and triggering the fourth global coral bleaching event. These impacts did not stop at the ocean; marine heatwaves have driven extreme weather patterns such as deadly atmospheric heatwaves and widespread flooding.
Results from this new study found that nearly 10% of the global ocean hit record-high temperatures during 2023-24, with devastating consequences for coral reefs, fisheries, and coastal communities. The team of researchers behind the study warn that as human-induced climate change accelerates, marine heatwaves will continue to worsen, and that more proactive action is needed to mitigate the damage that extreme ocean temperatures cause.
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. In addition, warmer ocean temperatures have driven species to migrate northward, increasing wildlife-watching tourism around the British Isles. The same elevated ocean temperatures also fuelled Storm Daniel, which brought catastrophic flooding to Greece, Bulgaria, and Turkey.
“The more regularly our marine ecosystems are being hit by marine heatwaves, the harder it is for them to recover from each event. As marine heatwaves continue to increase, we are likely to see further loss of marine species and ecosystems globally.” Shared Dr Katie Smith, Postdoctoral Research Assistant, and lead author at the Marine Biological Association of the UK.
Good forecasting and prompt action have helped reduced the impact of marine heatwaves in several regions. In Australia, for example, a quarter of the endangered red handfish population was safely moved into aquariums ahead of a marine heatwave, before being released again when waters cooled. In the USA, some coral and conch species were moved into deeper, cooler waters, helping to protect them from rising ocean temperatures. In Peru, the government provided financial support to fishers who were forced to suspend operations due to the closure of the anchovy fishery – a result of extreme heat conditions.
However, the response was not as swift or widespread in all regions. Improved forecasting and rapid response plans could have further reduced the impacts in other vulnerable regions.
While El Niño exacerbated the intensity of marine heatwaves in 2023-24, previous research has shown that human-induced climate change has already caused a 50% increase in marine heatwaves between 2011-2021. 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 now more important than ever.
Dr Katie Smith adds “Ultimately, to prevent marine heatwaves and their impacts from worsening, we need to reduce/stop our use of fossil fuels. In the interim, preparation for marine heatwaves and interventions to reduce loss of species have shown some success stories, but these are not permanent solutions.”
Read the full paper in Nature Climate Change.
