Extreme Coastal Waves due to Australian East Coast Lows in a Warming Climate

The southeast coastline of Australia is frequently impacted by East Coast Lows (ECLs) - hybrid storms with both tropical and extratropical characteristics. Although typically short-lived and spatially limited, ECLs can rapidly intensify and generate extreme waves that can cause severe coastal erosion and its associated hazards. Their small scale and transient nature make ECLs difficult to resolve in conventional global climate models. This study utilizes the HiRes-MESECA atmospheric dataset, comprising 12 historically significant ECL events between 2001 and 2016 that are re-simulated under an RCP8.5 climate scenario using a pseudo-global warming approach. Triple-nested WaveWatchIII modelling, that resolves waves to a spatial resolution of 100 m near the coast, was used to simulate ECL-driven waves at the 10 m isobath coastal boundary. The results of this near-coast wave modelling indicate that, contrary to prevailing expectations, future manifestations of these events may generate reduced peak wave heights, wave periods and overall cumulative wave power along southeast Australia, even considering an extreme (RCP8.5) climate change scenario. These findings challenge assumptions that climate change will necessarily intensify wave extremes globally and highlight the importance of incorporating regional-scale specifics into coastal hazard assessments and planning.