Interlinks between marine heatwaves, multi-hazard extratropical cyclones, meteotsunamis and phytoplankton blooms over Northwest Europe: insight from a km-scale regional coupled model

Climate change is bringing more marine heatwaves and more rainy extratropical cyclones, both trends already detectable. In parallel, storms are usually responsible for the ending of surface-based marine heatwaves. We employ a newly-developed regional coupled system at km-scale over Northwest Europe to show the relationships between marine heatwaves, storms and phytoplankton activity. We show that a marine heatwave amplified the rainfall, river flows, waves and surge of the most impactful storm of 2023 over the United Kingdom (storm Babet). We also show that storms terminating marine heatwaves can either increase or decrease phytoplankton activity, depending on seasonality. Finally, we show the high resolution, high frequency coupling system is also able to represent meteotsunamis (sub-tidal sea surface disturbances linked with slow-moving pressure disturbances), and opens a whole new area of research on compound convective systems and meteotsunami research. In addition to case-studies, we will present plans to use this coupled system across weather and climate time-scales, to increase our understanding and resilience to extreme compound events.