Climate science: Does the Great Barrier Reef affect rainfall in north Queensland?

Updated

Does coral create rain?

Climate scientists aboard the CSIRO's research vessel are leading a world-first study to understand how the Great Barrier Reef influences rainfall. The team of international scientists will also examine whether a dying reef will affect weather in north Queensland.

Coral's effect on weather patterns

Professor Zoran Ristovski squints his eyes to keep sight of a small drone that's zooming out across the sparkling blue waters of the Great Barrier Reef.

It is guided by two operators who work as a team. They're intently flying the craft along a predetermined path, making multiple manoeuvres aimed at ensuring it collects the right amount of air samples at multiple locations.

When the drone returns to the ship, its robotic legs extend down and like a mini-UFO it lands neatly on the deck, to the appreciative applause of scientists who have lined the upper rails of the CSIRO's research vessel, the RV Investigator, to get a good view of the display.

It is a sight that has been a long time coming for those working in this field of climate science.

Queensland University of Technology atmospheric scientist Professor Ristovski is the chief scientist on this voyage and is examining the air above the reef.

"The drones are carrying highly sensitive sensors," he explains.

"This is the first time to my knowledge that any kind of measurements like this have been done."

He is leading a world-first study by an international collaboration of climate scientists from 13 institutions that have come together on the voyage to confirm that coral creates rain.

For years, researchers have documented the increasing impact of climate change on the Great Barrier Reef, but very little is known about the reef's effect on the climate, particularly rainfall.

This team is here to investigate whether a damaged or dying reef could have repercussion for weather patterns in north Queensland.

"It is very, very important," Professor Ristovski says. "It has really far-reaching consequences."

Predicting the future

When corals and the algae that live on them are under stress, such as from higher water temperatures, they emit increasing amounts of a substance called dimethyl sulphide or DMS.

As the DMS molecules rise into the atmosphere, they are transformed into cloud seeding particles, and create low level clouds. When the particles have absorbed enough water, it rains … across the reef and over the farms and rainforests of North Queensland.

"This is fundamentally the most important process on the Great Barrier Reef," says Associate Professor Graham Jones, a marine chemist from Southern Cross University.

The scientists are investigating whether the process could be creating a climate feedback system — where heat-stressed coral cause clouds and rain — which then cool the sea surface temperatures.

And they're developing models that will help them predict what will happen in the future, as warming continues.

"With the increase in temperature of the ocean, if it doesn't die, the composition of the reef will change for sure, which will influence the emissions of the DMS," Professor Ristovski says.

"If we don't have the reef, we'll have less of these cloud seeds and we could have different rain patterns.

"This data will improve our models and allow us to predict the impact of climate change on the weather patterns in the future and will enable policy-makers to make informed decisions."

Professor Jones agrees: "If cloud cover and rainfall decrease, then we're going to see a major change in the climate of north and north eastern Australia."

Links to El Nino and La Nina

And the researchers believe the impacts could be far-reaching.

"The western Pacific has the highest biomass of coral reef on the planet, so if these coral reefs produce low level cloud as we suspect, then it has a major impact," Professor Jones says.

"There is a potential link between the severity of El Nino and La Nina.

"That is extremely important but at this point in time, we know nothing about that, or extremely little."

The climate scientists on this voyage of discovery are working to increase that level of knowledge.

They will spend this month, dipping instruments and sensors into the water and raising them in the air in search of answers, but their efforts to help shore up the future of the reef and the rainforests of north Queensland will continue long after they are back to being land lubbers.



The research

Australia's national research vessel, the RV Investigator was commissioned about 18 months ago and has been helping scientists gather data since then.

Twelve organisations are taking part in this four week research voyage, titled The Great Barrier Reef as a significant source of climatically relevant aerosol particles.

They include QUT, University of Melbourne, CSIRO, Southern Cross University, UTS, BOM, University of Wollongong, NIWA, NIES Japan, Fudan University, Auckland University of Technology, the University of Tsukuba and NOAA.

While the researchers on the ship are measuring DMS emissions in the water column and in the air, another team is working in a land-based mobile laboratory at Mission Beach, south of Cairns, analysing air samples as they come off the reef.

"The research will help us improve our understanding of the interaction between the biosphere and the atmosphere," Professor Ristovski says.

"One of the main aims is to collect data on the strength of the emissions from the reef, that we could then put into climate models and then model various scenarios, so off-reef, on-reef, turning the reef on and off to see if the rain pattern and rainfall in north Queensland will strongly depend on the reef.

"So will that hydrological cycle change if the reef dies off?"

He says the sea-borne effort to gather data is just the beginning.

"On the ship, we have 40 researchers and CSIRO support staff and on Mission Beach there's another five researchers, but we will need a team at least double that number of people to analyse all the data," he says.

"It takes a month to collect data, then a year to analyse data from each individual group, then at least another year to bring the water, air, climatology, meteorology together, that's going to be a massive task."

But the first data information will become available in 12 months.

"We've got number of collaborators from all around the world and the data that is collected on the ship with funding received from the Marine National Facility has to be made available to the public within a year," he says.

"So within a year we have to go to the data, crunch the data and then make it available to the whole scientific community, so they could run their models.

"So maybe someone will show something different or see something in the data that we missed, that's always possible."

The scientists would welcome the rigour into this new area of research.

Credits

Reporter: Kathy McLeish

Kathy McLeish Images: Dean Caton

Dean Caton Production: Heidi Davoren

Topics: science-and-technology, weather, environment, environmental-impact, qld

First posted