Waters off WA have been affected by prolonged marine heatwaves since September.
Regions off the north-west coast were hottest, with ocean temperatures 1.5˚C higher than average over a five-month period and sometimes 4˚C to 5˚C higher at the surface.
Analysis by the non-profit group Climate Central found climate change had made the marine heatwave 20 times more likely to occur – and the most affected period in November 100 times more likely. Heatwave conditions are triggered when an area is hotter than 90% of recorded temperatures for that time of year over at least five consecutive days.
Dr Andrew Pershing, the chief program officer at Climate Central, which has adapted climate attribution methods for studying major weather events on land to the ocean, said the escalating heat seen off the coast of WA was “not a normal event”.
“This is an event that is directly tied to burning fossil fuels,” he said.