Toward a mechanistic characterisation of marine heatwaves.

A mechanistic understanding of marine heatwaves (MHWs) requires robust frameworks for detection, tracking, and attribution. Conventional pointwise definitions, which identify MHWs pixel by pixel relative to fixed thresholds, have enabled global analyses but neglect the event-scale spatiotemporal evolution and underlying drivers. Recent kinematic approaches overcome the evolution issue by treating MHWs as evolving spatiotemporal objects. Here, we build on this framework by also considering the drivers. We examine the MHW dynamics by quantifying the scale and driver dependence of MHW objects, identifying dominant forcing mechanisms throughout their lifetimes, and characterising key features linked to distinct drivers. We further introduce a normalisation framework that preserves the event scale, while enabling composite analyses across multiple MHWs. Applying this approach to the Tasman Sea, a region of complex atmosphere-ocean interactions, we reveal distinct atmospheric and oceanic conditions that shape the MHW evolution at different stages. By explicitly linking evolving MHW entities to their physical drivers, our method advances the mechanistic characterisation of MHWs, enhances understanding of their spatiotemporal dynamics, and informs prospects for improved prediction.