Marine heatwaves are intensifying due to climate change, but the role of feedback mechanisms remains unclear. This study uses coupled climate simulations with observed atmospheric flow to analyze the 2019 Northeast Pacific marine heatwave under preindustrial, present-day, and +4°C warmer conditions. Results indicate that air-sea interactions, including reduced clouds and mixed-layer depth, amplify heatwave intensity and spatial extent. In a +4°C warmer climate, the heatwave's warming reaches +2.9 ± 0.15 °C above present levels, stressing marine ecosystems.

Marylou Athanase, Antonio Sánchez-Benítez, Helge F. Goessling, Felix Pithan, Thomas Jung