One of the most severe marine heatwaves on the planet is taking place in the shallow seas around the UK and Ireland. That’s according to the US National Oceanic and Atmospheric Administration (NOAA), which has labelled this a “Category 4” heatwave. Rarely used outside of the tropics, a cat 4 heatwave means “extreme” heat.
Marine heatwaves are classified as “prolonged periods of anomalously high sea surface temperature”, when compared to the long-term average for that time of year. And thanks to measurements made by satellites orbiting the earth we know that, in some areas around the UK, surface water temperatures are 4°C to 5°C above normal for mid June.
