CANBERRA (BLOOMBERG) - Australia's iconic Great Barrier Reef has suffered its third mass coral bleaching in five years, according to early results of aerial surveys over the World Heritage site.

"I saw coral bleaching both at the surface and as deep as 16 metres," the Climate Council said in a statement Thursday (March 26) citing Dean Miller from the Great Barrier Reef Legacy.

Miller has recently returned from assessing an area off Cooktown, with the council saying the evidence has been backed up by renowned scientist Terry Hughes, who is conducting aerial surveys this week over hundreds of individual reefs.

About the size of Japan, the Great Barrier Reef is the world's largest single structure made by living organisms and a popular tourist attraction. In 2018, it supported around 64,000 jobs and contributed about US $6.4 billion (S$9.2 billion) annually to the national economy.

2019 was Australia's hottest, driest year, according to data from the Bureau of Meteorology, which goes back to 1910. The average temperature last year was about 1.5 deg C above the 30-year mean, while rainfall dropped to its lowest in figures back to 1900.

That conditions exacerbated a years-long drought in much of eastern Australia, contributing to the summer's devastating wildfires that burnt out an area almost the size of England. The crisis placed renewed pressure on Prime Minister Scott Morrison's pro-coal conservative government to take more extensive action to tackle climate change, including punishing greenhouse-gas polluters.

Miller said the "very hot summer" had contributed to water temperatures on the Reef rising up to 2 deg C above normal.

"While the bleaching is extensive, fortunately tourism hot spots around Cairns and Port Douglas have been spared this year," he added.