To slow the speed at which high temperatures and warm waters bleach the corals of the Great Barrier Reef, Australian scientists are spraying droplets of ocean water into the sky to form protective clouds.
Researchers working on the Cloud Brightening project said they used a turbine* to spray microscopic* sea particles* to thicken existing clouds and reduce sunlight on the world’s largest coral reef ecosystem*, located off Australia’s northeast coast.
The water droplets evaporate*, leaving only tiny salt crystals which float up into the atmosphere, allowing water vapour to condense around them, forming clouds.
“If we do it over an extended period of time for a few weeks to a couple of months, when the corals are experiencing a marine heatwave, we can actually start to lower the water temperature over the reef,” said project leader and senior lecturer at Southern Cross University, Dr Daniel Harrison.
The project had its second trial in March – at the end of the Australian summer when the reef is at its hottest – gathering valuable data on the atmosphere when corals are most at risk of bleaching.
A combination of light and warm water causes coral bleaching. By cutting light over the reef by 6 per cent in summer, “bleaching stress” would be cut by 50 to 60 per cent on the undersea ecosystem, Dr Harrison said.
Cloud Brightening project
But the benefits of cloud brightening would lessen over time unless other measures slowed climate change.
“If we do have really strong action on climate change, then the modelling shows that the cloud brightening is enough to stop the reef declining and to actually see it through this period while we reduce our carbon emissions,” Dr Harrison said.
One of Australia’s best-known natural wonders, earlier this year the Great Barrier Reef came close to being listed as an endangered World Heritage Site by the United Nations, but the Australian government successfully lobbied* against the status downgrade.
The cloud brightening project is supported by the partnership between the government’s Reef Trust and the Great Barrier Reef Foundation.
An initial trial of prototype* equipment in 2020 proved it was feasible* to pump seawater and atomise* it into tiny droplets at a rate of hundreds of trillions per second.
“It’s effectively boosting a natural process because cloud droplets form over the ocean when moisture gathers around salt crystals and other minute particles, stirred up by winds from the ocean’s surface,” Dr Harrison said.
“This year what we were really interested in looking at was the behaviour of that plume of sea salt droplets as it drifted away from the boat and mixed towards the clouds. We hope this critical information we’ve collected will help us to design a system for the future that will enable us to show a brightening response in the clouds.”
Both expeditions were both conducted at Broadhurst Reef, 100km offshore from Townsville on the central section of the reef. It involved researchers from Southern Cross University and QUT in partnership with organisations including the Sydney Institute of Marine Science (SIMS), the University of Melbourne, the University of Sydney and the Australian Institute of Marine Science.
Dr Harrison said cloud brightening had the potential to protect the entire Great Barrier Reef from coral bleaching in a relatively cost-effective way, buying precious time for longer-term climate change mitigation*.
“What’s unique about this technique is that can be used intermittently* when required as an emergency response to protect corals from bleaching during marine heatwaves,” he said.
Great Barrier Reef Foundation managing director Anna Marsden said it was crucial to pioneer new techniques to help save the reef from a growing combination of threats.
“The greatest threat to our reef is climate change and we’re already seeing the effects, with three mass bleaching events in five years,” Ms Marsden said.
“The rate at which bleaching events are now occurring on the reef is a matter of huge concern but there is hope, and the time to act is now.”
Manduburra traditional owner Usop Drahm, who joined both expeditions, said he welcomed the scientific research, which had seen Indigenous people and other Australians work together to maintain the Reef ecosystem for future generations.
“This technology might help prevent bleaching and we like that it uses no chemicals and relies on natural processes,” Mr Drahm said.
- turbine: machine using air, water, steam or hot gas to turn a wheel to produce mechanical power
- microscopic: tiny, so small it can only be seen through a microscope
- particles: a very small piece of matter, a minuscule or tiny amount of something
- ecosystem: a community of plants, animals, and other organisms and their surrounding environment
- evaporate: turn from liquid into vapour
- prototype: early sample, model or version
- feasible: possible, likely, achievable
- atomise: break up into very small units, convert into very fine pieces or droplets
- lobbied: sought to influence others on an issue
- mitigation: reducing the significance, importance or severity of something
- intermittently: at irregular intervals
- What did scientists use to spray the microscopic sea particles?
- What is left once the water droplets evaporate?
- Where were both expeditions conducted?
- What did an initial trial using prototype equipment prove?
- According to Dr Harrison, what is unique about this technique?
LISTEN TO THIS STORY
1. Explain cloud brightening
Draw a diagram or create a short video to explain how the process of “cloud brightening” works and how it benefits the Great Barrier Reef.
Hint: if you choose to make a video, consider using props to help show what you mean in your explanation.
Time: allow 20 minutes to complete this activity
Curriculum Links: English; Science; Sustainability
Use a highlighter to identify all of the evidence in the story that tells us that cloud brightening, while helpful, is not considered the long-term solution to coral bleaching.
Time: allow 10 minutes to complete this activity
Curriculum Links: English; Science; Sustainability
I spy nouns
Nouns are places, names (of people and objects), and time (months or days of the week).
How many nouns can you find in the article? Can you sort them into places, names and time?
Pick three nouns and add an adjective (describing word) to the nouns.