Abstract
As marine heatwaves (MHWs) become more intense and longer lasting due to global warming, understanding the drivers and impacts of these events is crucial for effective marine resource management. This study investigates the influence of El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), Southern Annular Mode (SAM), Sub-Tropical Ridge High (STRH), and Madden Julian Oscillation (MJO) on sea surface temperature (SST) anomalies and MHWs around Australia. The aim of this research is to improve our understanding of the drivers of MHWs on sub-seasonal to seasonal (S2S) timescales, which bridges the gap between short-term weather and interannual to long-term climate variability. By analysing SST anomalies and MHWs characteristics during specific driver phases, a simple MHW hazard index is developed. Our findings support previous research indicating that La Niña plays a role in driving MHWs off the coast of Western Australia and reveals a previously unrecognised connection between ocean warming off Queensland and Tasman Sea low-pressure systems associated with the negative phase of the STRH. Our research emphasizes the importance of considering multiple drivers and their compounding effects on MHWs by showing significant changes to typical La Niña MHW patterns with the additional influence of the MJO. By considering drivers acting in the S2S timescale, forecasts can more accurately capture the timing, intensity, and spatial extent of MHW events within a season. These improved forecasts can enhance the ability of marine managers to adapt and allocate resources based on evolving climate conditions, enabling effective implementation of harm minimisation strategies.