More frequent, longer, and hotter consecutive marine and terrestrial heatwaves in China's coastal regions.

Marine heatwave (MHW) can increase heat exchange between the land and the ocean, which may further develop into a consecutive marine and terrestrial heatwave (CMTHW). Despite their significance, the feedback mechanisms underlying these compound events remain inadequately understood. This study provides a comprehensive analysis of the interactions between terrestrial and marine heatwaves across China's coastal regions, leveraging multiple temperature datasets. Our findings reveal a marked increase in both the frequency and spatial extent of CMTHWs over the past four decades. Notably, longer lasting and more intense MHWs are more likely to trigger subsequent terrestrial heatwaves (THWs), indicating that CMTHWs are associated with more severe and prolonged MHWs compared to standalone MHWs. Atmospheric processes cause additional land surface warming relative to the ocean. Specifically, during CMTHWs, land surface latent heat flux anomalies are significantly larger than those over the ocean, highlighting the critical role of atmospheric feedback. These findings underscore the need for further investigation into the mechanisms linking marine and terrestrial heatwaves and the broader implications for coastal climate dynamics and ecosystem resilience.