Scientists have expressed concern after sea surface temperatures off France’s Atlantic coast surged to unusually high levels, reaching values typically seen during the peak of summer.
According to researchers, some areas recorded a dramatic increase of up to 6.9°C within a week, making it one of the most significant marine heatwave events observed in recent years.
Sea temperatures reach August-like levels
Coastal areas including Gironde and Vendée have reported sea surface temperatures ranging between 22°C and 23°C, despite it being only early June.
Experts say these temperatures are more commonly recorded in August and have followed an intense spell of heat across western France, where several hundred air temperature records were broken in recent days.
Marine heatwave specialist Thibault Guinaldo of Météo-France described the warming as exceptional, noting that oceans generally heat up much more slowly than land due to their high thermal inertia.
Heatwave breaks previous ocean records
Scientists reported temperature anomalies of up to 5°C above seasonal averages across parts of the Atlantic coast and the Bay of Biscay.
Researchers said the current event has exceeded marine temperature records set in 2022 and is approaching levels observed during the major marine heatwave of June 2023.
The rapid warming has been linked to a combination of extreme air temperatures, intense sunshine and favourable ocean conditions that accelerated surface heating.
Marine ecosystems could face stress
Although temperatures on land have started to decline, ocean temperatures are expected to remain significantly above normal in the coming days.
Environmental experts warn that prolonged marine heatwaves can disrupt ecosystems, affecting fish populations, shellfish, plankton and other marine species sensitive to temperature changes.
Scientists are continuing to monitor the situation closely as concerns grow over the increasing frequency and intensity of marine heatwaves associated with climate change.