Plymouth study finds rising seafloor temperatures pose a risk to marine life
'Marine heatwaves' are becoming 50% more frequent
Last updated 23rd Aug 2025
A new study by the Plymouth Marine Laboratory shows that marine heatwaves on the seafloor could be more than 50% more frequent in future than at the surface of the ocean during hot summer months.
Experts say this is a concerning prospect for bottom-dwelling species that cannot escape the rising temperatures, with ripple effects across entire ecosystems and humans alike.
What is a marine heatwave?
A period lasting at least 5 days where sea temperature is greater than the 90th percentile of historical temperatures for that time of year.
Led by PML’s Dr Robert J. Wilson, the study investigated how marine heatwaves will change in the future on the northwestern European shelf, a vital marine ecosystem that provides ecological, cultural and economic services to many countries.
The northwestern European shelf is typically defined more by seabed topography (shallow continental shelf waters) than by strict political or oceanographic boundaries, and generally includes:
- North Sea – between the UK, Scandinavia, Germany, the Netherlands, Belgium, and France
- English Channel – between southern England and northern France
- Celtic Sea – southwest of Ireland and west of Cornwall
- Irish Sea – between Ireland and Great Britain
- Bay of Biscay – off the western coast of France and northern Spain
- Parts of the Norwegian Sea – particularly its shallower southern/shelf-edge areas
- Shetland–Orkney waters and surrounding shelf areas north of Scotland
Marine heatwaves, which are periods when ocean temperatures are unusually high for that time of year, are becoming more frequent and severe due to climate change. These extreme events harm ocean life by pushing temperatures beyond what many species can tolerate.
Until now, most studies have focused on heatwaves at the ocean surface, but little has been known about what may happen on the seafloor in the future. Using state-of-the-art regional climate models, Dr Wilson and colleagues from Plymouth Marine Laboratory and the National Oceanography Centre found that heatwaves will become much more common, especially at the seafloor, where natural temperature changes are usually smaller.
Dr Wilson concludes:
“Until now, we have largely predicted future marine heatwave rates based on what will happen on the sea surface. We have shown that this can be highly misleading for critical European seafloor ecosystems, where climate change will cause more frequent extreme temperatures than at the sea surface. It is therefore critical that marine heatwave monitoring and assessment move beyond the surface and shift to a 3D view of the ocean.”