By analyzing more than three decades of atmospheric weather, Monash University in Australia has identified easterly trade winds as a key cause of mass coral bleaching events in the Great Barrier Reef.
Trade wind temperature regulation
The research was a case study of a mass bleaching of 91% of the reef in February 2022, the fifth in eight years, that provided the breakthrough for lead researcher and Monash atmospheric science PhD candidate Lara Richards.
The findings, detailed in a peer-reviewed study published in the Scientific Reports scientific journal on Saturday October 12, highlight the exacerbating impact of local meteorology on coral reefs and provide clues to help combat the impact of coral bleaching on the reef.
Drawing on data from the Australian Institute of Marine Science’s Davies Reef automatic weather station at Davies Reef, 100km northeast of Townsville, Monash researchers compared 30 years of ocean and air temperature, humidity, wind speed and direction, and wave and tidal pattern.
“Our research has identified that it was the collapse of the trade winds that drastically altered the near-surface temperature of the ocean,” Richards said. “During a three-week period, we observed the ocean warming in this area by almost 2°C to 30.5°C, as the absence of the trade winds allowed a decrease in cloud cover, increase in solar radiation, and lack of evaporative cooling. Following the re-establishment of the trade winds, the warming ended abruptly and the ocean temperature cooled by 1C over 48 hours as evaporative cooling effectively tripled.”
Local meteorology versus El Niño
The reef is a key tourist destination, and its loss would place an estimated 64,000 jobs and US$56m in revenue in jeopardy. Previously, the cause of the spike in ocean temperatures resulting in coral bleaching had been unclear and was often linked to El Niño. However, by identifying the cause of key incidents of ocean temperature increases that cause coral bleaching, the researchers hope to dispel myths around links to El Niño.
“People tend to associate coral bleaching on the Great Barrier Reef with El Niño, which we’ve now been able to demonstrate is misinformation,” Richards said. “That’s why we were looking at 2022 in particular because it was the first bleaching on the reef during a La Niña phase. So, we were able to show that as bleaching can occur during both El Niño and La Niña, it was the change in the meteorological conditions that caused the bleaching.”
“The United Nations’ Intergovernmental Panel on Climate Change has identified the loss of coral reefs as a key risk for Australia, so understanding them is critical to being able to predict and respond to them,” Richards said. “Now that we understand the conditions that can lead to bleaching events, we will be able to predict where and when they will occur and put in place measures to respond to and mitigate their impacts.”
For more of the top insights into the meteorological significance of coral reefs, read ‘University of Arizona’s Diane Thompson explains what coral reefs can reveal about the future’, here.
