Highest ocean heat in four centuries places Great Barrier Reef in danger

NEWS - Australia’s Great Barrier Reef is facing critical danger from back-to-back extreme ocean heatwaves. The latest 400-year temperature record shows the ecosystem is facing catastrophic damage as warming sea temperatures and mass coral bleaching events threaten to devastate the ecology, biodiversity and beauty of the world’s largest coral reef.

Ocean temperatures in the Coral Sea are at their highest in four centuries. Researchers drilled into coral skeletons from within and around them to analyse the chemical makeup of the samples to reconstruct sea surface temperatures from 1618 to 1995, alongside modern instrumental sea level measurements spanning 1900 to 2024.

Ocean temperatures in the region were relatively stable before 1900, but from 1960 to 2024 they have been rising relentlessly. The increase is linked to human greenhouse gas emissions, the team found. The years 2016, 2017, 2020, 2022 and 2024 were all warmest on record, with temperatures up to 1C warmer than average. Every year, mass bleaching events occur during the warmest months of January to March.

“The Great Barrier Reef is an icon,” says Benjamin Henley of the University of Melbourne in Australia.

Highest ocean heat in four centuries places Great Barrier Reef in danger 2

Global warming threatens up to 90 percent of the world’s coral reefs. UNESCO designated the reef a World Heritage Site in 1981. The UN agency had considered adding the reef to its World Heritage in Danger list. In 2023, UNESCO delayed the move because of the Australian government’s pledge to improve protection.

“The more emissions we reduce now, the better it will be not just for the Great Barrier Reef, but for society,” says Helen McGregor of the University of Wollongong in Australia.

Original research

Henley, B.J., McGregor, H.V., King, A.D. et al. Highest ocean heat in four centuries places Great Barrier Reef in danger. Nature 632, 320–326 (2024). DOI:10.1038/s41586-024-07672-x

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