Experts fear for health of corals and other marine life as about 1m sq km of ocean experience prolonged elevated temperatures

A marine heatwave has broken out along more than 2,000km of the Queensland coast, raising concerns for the health of corals on the Great Barrier Reef and other ocean life.

The Bureau of Meteorology briefed the Great Barrier Reef Marine Park Authority about the raised ocean temperatures on Friday.

A marine heatwave happens when temperatures over an area are in the hottest 10% ever recorded for that time of year and then stay there for at least five days.

Dr Alex Sen Gupta, an associate professor at the UNSW Climate Change Research Centre and marine heatwave expert, said: "If you look globally, we’re seeing more marine heatwaves now than we have ever seen before."It’s exceptional at the moment.

Dr Jessica Stella, the assistant director of reef health at GBRMPA, said there was still an element of the unknown about the effects of a heatwave in winter, when overall temperatures are cooler than in the summer.