Ocean temperatures expected to reach highest level in a decade as CSIRO prediction proven accurate

Headshot of Liam Beatty
Liam BeattyMidwest Times
A diver examining the isolated Scott Reef which lost almost all its corals to bleaching when ocean temperatures rose in 1998.
Camera IconA diver examining the isolated Scott Reef which lost almost all its corals to bleaching when ocean temperatures rose in 1998. Credit: Nick Thake/PR IMAGE

As hot temperatures cause raging bushfires across WA, a marine heatwave predicted by the CSIRO has been confirmed by real-time observations.

Ocean temperatures along the WA coastline have begun rising this month and are expected to reach their highest level in a decade by April, peaking at 1C above average along the coastline.

Dr Alistair Hobday, pictured, the CSIRO marine scientist leading the research, said a figure of 1C warming was an average for the whole coastline but it could be up to 3C warmer close to the shore.

Dr Alistair Hobday.
Camera IconDr Alistair Hobday. Credit: Paul Redding/Supplied

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Last week, he told the Midwest Times real-time data had confirmed marine temperatures had begun to rise and would have “significant effects on the marine ecosystem”.

“Using data up until the end of November, we predicted a marine heatwave beginning in early January,” he said.

“It’s begun this week ... it’s exciting to see the results line up.”

A marine heatwave is defined as five or more days when sea surface temperatures are warmer than 90 per cent of previous observations at the same time of year.

The waters off WA met that threshold last week. The forecast was the first time machine-learning had been used to predict marine temperatures in advance.

The forecast was created as a proof of concept, but Dr Hobday said he was hoping this would become an annual prediction for the summer months — when the most “intense” changes are seen.

The heatwave, he believes, will have an impact on coastal ecosystems, with coral bleaching a possibility along the Pilbara coast and northern Ningaloo, and tropical fish species heading south.

“In the Mid West, coral will do well with warmer temperatures,” he said. “But further up, we could see coral bleaching occurring.”

The forecast predicted ocean temperatures could reach the highest level since the 2011 marine heatwave event which has widespread impacts on ecosystems and fisheries.

Fisheries including crabs, abalone and scallops were devastated off the Mid West and Gascoyne coast during the event when water temperatures soared up to 5C above normal.

The event was also blamed for widespread coral bleaching from Ningaloo to Shark Bay, with seagrass meadows damaged and a significant increase in shark activity in the region. Some areas have still not recovered.

Dr Hobday said a marine temperature forecast had exciting applications for governments, commercial operations and conservationists, but it was up to users to work out how it could be applied.

“All kinds of ocean users make use of different lead times, which is what we can now provide,” he said.

“For example, a fisherman may look at the forecast over the next few days and make the decision to wait until the water is warmer.

“Similarly, conservationists may delay restoration efforts this year for Shark Bay’s seagrass meadows because of the heatwave.

“I like to think this poses the challenge to key players. Now we can predict a marine heatwave what can we do to mitigate the effects?”

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