Nearly 10% Of Planet's Oceans Hit Record High Temps In 2023-24; Add-On Impacts, Especially Storms, Cost Billions
The world’s oceans experienced three-and-a-half times as many marine heatwave days last year and in 2023 compared with any other year on record, a study has found. 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, according to the paper published on Friday in Nature Climate Change.
Like heatwaves on land, a marine heatwave is defined as a period of higher than normal temperature over a longer than usual time. The most recent of these were brought about by human-induced climate change and amplified by El Niño conditions, the report’s authors said, with nearly 10% of the ocean hitting record high temperatures in 2023-24.
“The more regularly our marine ecosystems are being hit by marine heatwaves, the harder it is for them to recover from each event,” said lead author Kathryn Smith from the UK’s Marine Biological Association. Higher ocean temperatures “supercharge” evaporation, the study said, fuelling storms such as Cyclone Gabrielle which hit New Zealand in February 2023, killing 11 people and costing an estimated NZ$14.5bn (about £6.5bn).
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The effect on species was often devastating. Whales and dolphins venture closer to shore when the water is warm because they follow their prey, so this increased their chances of stranding, said Smith. For Mediterranean fan mussels, which have been dying in their millions since 2016, marine heatwaves may be the final nail in the coffin because the warming waters bring increased risk of diseases, the study said. Although human intervention saved some marine life from the recent heatwaves, the study found damage reduction was mostly lacking, possibly due to limited resources, disconnects between organisations and poor communication. When there was time to prepare, 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.
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https://www.theguardian.com/environment/2025/feb/28/surge-in-marine-heatwaves-record-temperatures-costs-lives-and-billions-in-storm-damage-study
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