Marine heatwaves are autocorrelation events exceeding a given  threshold for a given minimum duration. Marine heatwaves are driven locally by heat fluxes through the surface of a given volume, for example incoming solar radiation at the ocean surface, and horizontal advection of warm water within. Local drivers are, however, the consequence of weather systems and super-regional phenomena like teleconnections. Marine heatwaves can further be closely tied to extreme temperatures, with far-reaching consequences for ecosystems as for example coral reefs. This thesis is concerned with drivers of marine heatwaves, from local to super-regional, and furthermore with the attribution of extreme temperatures as cause for the decline of specific ecosystems.