Wind influences reef bleaching
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Wind patterns have emerged as a key factor in coral bleaching on the Great Barrier Reef.
Previously, bleaching was commonly linked to El Niño events, but a new study shows that a collapse of easterly trade winds - which drives ocean warming - also triggers bleaching.
The study focused on the severe bleaching of 91 per cent of the reef in February 2022, during a La Niña phase, which prompted a shift in understanding.
Lead researcher Lara Richards from Monash University found that the absence of trade winds caused ocean temperatures to increase by nearly 2°C, reaching 30.5°C due to less cloud cover, increased solar radiation, and reduced evaporative cooling.
“The collapse of the trade winds drastically altered the near-surface temperature of the ocean,” Richards said.
When the trade winds resumed, the ocean cooled by 1°C within 48 hours, underscoring their critical role.
“The return of the trade winds tripled evaporative cooling, bringing temperatures back to normal,” Richards added.
Her study analysed over three decades of data from the Davies Reef weather station, 100 km northeast of Townsville.
The researchers found local meteorology - specifically wind speed and cloud cover - were key drivers of temperature changes, rather than broader climatic phenomena like El Niño or La Niña.
This challenges existing assumptions.
“Bleaching can occur during both El Niño and La Niña phases, with local weather conditions being the main triggers,” Richards said.
The Great Barrier Reef has suffered five mass bleaching events since 2016, significantly impacting marine biodiversity and risking 64,000 jobs and $56 million in annual tourism revenue.
The United Nations’ Intergovernmental Panel on Climate Change (IPCC) identifies coral loss as a critical risk for Australia.
The findings not only clarify the role of local weather patterns but also offer a pathway for better forecasting and mitigation strategies.
“Understanding these conditions allows us to anticipate events and develop targeted responses,” Richards said.
The 2022 case study also uncovered connections between local meteorological conditions and broader weather patterns, such as the anticyclonic wave breaking linked flooding in the NSW town of Lismore.
The experts say it illustrates the need for more research into synoptic meteorology's impact on reef temperatures, as variability across different bleaching events suggests that outcomes may differ by region.