A group of scientists, led by Curtin senior research fellow Dr Jens Zinke, have researched the cause of marine heatwaves off the Western Australian coast by reconstructing a history of sea surface temperatures in the area.
The research suggests that these marine heatwaves are most likely caused by a negative Western Pacific Gradient, a combination of warm sea surface temperatures over the west Pacific Ocean and cool sea surface temperatures over the central Pacific Ocean, which is amplified by La Niña events.
The team have discovered that the negative Western Pacific Gradient has contributed to warming in the southeast Indian Ocean, including the west Australian shelf, resulting in marine heatwaves and coral bleaching along Western Australia’s coral reefs, as well as high sea levels off southwest Western Australia.
“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” says Dr Zinke.
Dr Zinke, who over the past 15 years has been studying coral reef systems in the Indian Ocean as recorders of environmental and climate change, conducted the research along with scientists from The University of Western Australia, CSIRO, the Australian Institute of Marine Science and the University of California, Santa Barbara.
Much like tree-ring dating, the scientists’ findings were determined by analysing annual growth bands within coral cores obtained from Ningaloo Reef, the Rowley Shoals and the Houtman Abrolhos Islands.
The resulting data allowed the scientists to reconstruct the sea surface temperatures off the west Australian shelf over the course of 215 years, from 1795 to 2010.
The team suggests that global climate change, the strong Western Pacific Gradient and an increased magnitude of thermal stress anomalies off the Western Australian coast could spell further impacts to the State’s coral reef ecosystems.
Their findings have been published in the international, peer-reviewed journal, Nature Communications.
For more information, read the article: Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient.