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Coral Cores Reveal Increasing Severity of Climate Events

Cores taken from the most southerly reefs off the coast of Western Australia have provided a 215-year history of sea levels, sea surface temperatures and ocean currents.

Scientists from the Australian Institute of Marine Science, The University of Western Australia, CSIRO and the University of San Diego examined samples of massive Porites colonies from the Houtman–Abrolhos Islands, which are directly in the path of the Leeuwin Current. “We obtained records of past sea temperatures by measuring the chemical composition of the coral skeleton from year to year,” said Dr Jens Zinke of UWA’s Indian Ocean Marine Research Centre. “This showed how changing winds and ocean currents in the eastern Indian Ocean are driven by climate variability in the western tropical Pacific Ocean.”

La Niña events in the tropical Pacific result in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off the south-west coast of Western Australia. “A prominent example is the 2011 heatwave along WA’s reefs, which led to coral bleaching and fish kills,” said Dr Ming Feng of CSIRO.

The team found that in addition to warming sea-surface temperatures, sea-level variability and the strength of the Leeuwin Current have increased since 1980.

The coral cores also reveal that the strong winds and extreme weather of 2011 off Western Australia are highly unusual in the context of the past 215 years. The authors concluded that this is clear evidence that global warming and sea-level rise is increasing the severity of these extreme events.

“Given ongoing global climate change, it is likely that future La Niña events will result in more extreme warming and high sea-level events with potentially significant consequences for the maintenance of Western Australia’s unique marine ecosystems,” said Dr Janice Lough of AIMS.

The research was published in Nature Communications.