Marine heatwave intensified impacts of Storm Babet by 9-20%, new study finds

The study, ‘Marine heatwave amplifies extreme multi-hazards of extratropical cyclone Babet’, published in the Natural Hazards and Earth System Sciences journal, finds that unusually warm sea temperatures increased rainfall, river flows, storm surge and wave energy during the storm, amplifying impacts by between 9% and 20%. 

Findings demonstrate that marine heatwaves can impact weather on land. Waters around the UK are currently experiencing widespread marine heatwave conditions, which earlier in July reached up to Category 4, classified as “extreme”, a level rarely recorded in UK waters. This is linked with recurrent atmospheric heatwaves, bringing long-lasting sunny and calm conditions for the third time this year, giving sea surface temperatures little opportunity to cool. 

Marine heatwave added energy to the atmosphere 

The study provides the clearest evidence to date that marine heatwaves in the North Sea can act as amplifiers of UK storm hazards, driving increases in rainfall, river flows, storm surges and coastal wave energy. 

Lasting almost seven weeks, from 1 September to 21 October 2023, the North Sea marine heatwave warmed the full depth of the shallow basin by around 0.8-1 °C. These unusually warm conditions resulted from persistent anticyclonic weather, allowing the ocean to absorb and retain excess heat. 

Storm Babet induced a low-level wind jet, a fast-moving stream of air close to the ground that helps storms grow stronger. As the wind jet came from the east, bringing heavier rain than usual to many areas, the warmer than average waters: 

• Increased evaporation and added extra moisture to the atmosphere, contributing to around 5% heavier rainfall over eastern Scotland during the storm 
• Deepened the storm slightly, lowering central pressure by around 1-2 hPa compared to a cooler ocean scenario, indicating a modest but measurable intensification 
• Enhanced atmospheric instability, strengthening the low-level jet 

Warm seas as a ‘hazard amplifier’ 

For the first time, researchers used the UKC4 configuration, the Met Office’s state-of-the-art, kilometre-scale regional coupled modelling system that brings together detailed simulations of the atmosphere, land, ocean and waves into a single framework. This was made possible by the Met Office’s supercomputing capacity. 

Unlike traditional approaches that model these elements separately, UKC4 allows them to interact in real time, capturing the two-way exchange of heat, moisture and momentum between the sea and the atmosphere. Covering the UK and surrounding shelf seas at high resolution, it also integrates land processes such as river flows, enabling scientists to assess multiple hazards together. 

Researchers compared the real heatwave event with a scenario in which the North Sea had been cooler. The warm sea conditions were found to have amplified several key hazards associated with Storm Babet, including:  

• River flows, up by 12-18%, increasing flood risk 
• Storm surge, 20% higher 
• Coastal wave power, strengthened by around 9% 

These enhanced hazards contributed to significant inland and coastal impacts. Storm Babet caused five years' worth of erosion in coastal places, generated inland floods, threatened oil rigs to lose anchor and stranded marine life. 

A blocking area of high pressure over Scandinavia prevented the storm from moving east into the North Sea, leaving rain fronts stalled over eastern Scotland for an extended period before shifting back across England and Wales. This configuration also meant strong winds were blowing from Denmark to Scotland for three days across the North Sea, generating powerful waves and sustained tidal surge on the east coast of Scotland. 

Growing influence of marine heatwaves 

Dr Ségolène Berthou, Air-Sea Interaction Specialist at the Met Office, and report author, said: “Over 90% of the excess heat generated by greenhouse gas emissions has been absorbed by the global ocean. The upper layers alone store as much heat as the entire atmosphere. This long-term warming is reflected in the rising occurrence of marine heatwaves, and the near disappearance of marine cold spells. Without significant reductions in global emissions, near permanent marine heatwave conditions around the UK could emerge as early as mid-century.  

“As our oceans warm, research like this provides crucial insight into how UK weather hazards are evolving. Enhanced modelling allows us to anticipate these interactions more effectively and support national resilience in a changing climate.” 

Piyali Goswami, PhD researcher for the Department of Meteorology at the University of Reading, and report author, said: “Marine heatwaves are becoming more frequent as the climate continues to warm. In shallow shelf seas such as the North Sea, accumulated heat cannot dissipate into the deeper ocean, increasing the likelihood that future storms with similar characteristics to storm Babet will interact with unusually warm waters.  

“This research highlights how warmer seas can change the character of UK storms. Even relatively small increases in ocean temperature can alter storm behaviour in ways that meaningfully affect rainfall, flooding and coastal hazards.” 

Storm Babet was one of the UK’s most disruptive storms of that year and brought exceptional rainfall to parts of eastern Scotland, with 150 to 200mm falling in the wettest areas and the Met Office issuing two red severe weather warnings for rain.