Marine heatwaves to become more frequent off UK and Irish coasts, experts say

Scientists find 10% chance that similar events to the ‘unheard of’ temperatures in 2023 could occur each year Helena Horton Environment reporter Tue 7 Oct 2025 11.00 CEST

The unprecedented marine heatwave of 2023 was in line with climate modelling, research shows, as scientists warn such events will become more frequent.

The “unheard of” heatwave off the UK and Irish coasts during a summer of 40C temperatures raised concerns that fish, shellfish and kelp would not be able to survive.

During the heatwave, temperatures in the shallow seas around the UK, including the North Sea and Celtic Sea, reached 2.9C above the June average for 16 days. The extended period of time put sea life at risk of death.