By Angus Dalton
The recent far-flung adventures of Australia’s flagship research vessel include eavesdropping on blue whale song in the Antarctic, chasing storms across the Top End and uncovering a tropical shark graveyard of 750 teeth, one of which fell from the gum of an ancient shark.
But the RV Investigator’s 101st expedition will take place just off Sydney.
The CSIRO’s flagship research vessel has made a rare stop in Sydney, at Balmain’s White Bay, ahead of its 101st expedition.Credit: Brook Mitchell
Next week, the CSIRO’s $126 million, 11-storey floating laboratory will charge out between the heads of the harbour to begin crucial work scrutinising mesocale eddies – gigantic, hot swirls of ocean water.
These “underwater cyclones” are poorly understood, yet exert a profound influence on the nation’s weather and food security. More than half of the ocean’s kinetic energy is made up of eddy movement as they mix heat, nutrients, salinity and carbon through the seas.
Voyage chief scientist Professor Moninya Roughan is leading a team of 22 scientists seaward to study the “eddy field” off NSW generated by the East Australian Current, the surge of tropical warm water that barrels down the eastern coast.
“They’re big and they’re hot,” Roughan, a professor of oceanography at UNSW, says from the control room of the Investigator, which is currently moored in Balmain’s White Bay. “And we don’t really understand where they move, or why, or how.
Mesoscale eddies cover the ocean, shifting heat and nutrients alongside larger, stronger currents.Credit: NASA's Goddard Space Flight Center
“We’re also trying to understand how deep these eddies go, how much heat they hold, what their structure and shape is, and how they evolve in time.”
The current once split off towards New Zealand near Forster. But as the climate heats, the EAC is ushering hot tropical water further south beyond Sydney, intensifying marine heatwaves and driving species of lobster, urchin and manta ray towards Tasmania.
The $2.5 million mission will scrutinise how these 100-kilometre-wide underwater cyclones behave in one of the planet’s fastest-warming slabs of ocean, and the effects of the convection they vent up into the atmosphere.
If the ship begins to rock, winds rattling the metal benches of the vessel’s 12 laboratories and making for some seasick scientists, the expedition’s atmospheric team will be cheering. They’re hoping to collect live data from a brewing thunderstorm to probe how the eddies unleash rain, hail and lightning on Australia’s south-east.
A view from the porthole of the RV Investigator ahead of its 101st expedition.Credit: Brook Mitchell
Roughan’s findings will also be important for fisheries. When hot and cold eddies clash, Roughan suspects their intersection creates productive hotspots as the colder, nutritious water mixes with warm. Tuna gather in the centre of eddies, relaxing in the warm oases and feeding on the nutrient-laden swirl.
The navy is also paying attention to the expedition; eddies can cloak submarines from enemy sonar, concealing subs in their enormous whirls of stewing water.
Hunting mesocale eddies will involve a brand-new $1 billion satellite and an array of floating buoys that will hint where these underwater cyclones may be spinning around the Investigator.
Behind the vessel, a piece of equipment called the Triaxus will trail a kilometre of wire gyrating through the water column and taking sensitive measurements of heat and salinity through the eddies.
Margot Hines, the voyage manager, with the CTD which can plunge 5000 metres beneath the waves and collects “snapshot” samples of the deep ocean. Piecing the data together will reveal more about the depth and movement of eddies.Credit: Brook Mitchell
Another apparatus called the CTD (standing for conductivity, temperature and depth) will plunge 5000 metres below the surface. It’s a ring of 36 bottles that can snap shut at any time, capturing a discrete sample of ocean water at a range of depths for hydrological analysis.
“There are a lot of challenges associated with observing the ocean,” Roughan says. “Instruments have to withstand great pressure to get down that deep, and then they have to return all their information to the surface. It’s a corrosive environment, the salt destroys everything.”
While the Investigator patrols the seas, NASA’s new SWOT (Surface Water and Ocean Topograph) satellite will provide backup from space, mapping the ocean around the vessel at high resolution to help track down and analyse the eddies.
“Getting that in very high resolution, and very near real time, is game changing,” Roughan says.
Voyage chief scientist Professor Moninya Roughan (left) and Margot Hines on the bridge of the Investigator.Credit: Brook Mitchell
A white sphere above the vessel’s bridge acts as a live weather station, beaming back climate data to the Bureau of Meteorology, and researchers will also dunk nets into the ocean to collect plankton and bluebottle specimens.
And the Investigator never takes the same path twice. The hull carries an acoustic mapping gondola, as part of an ambitious effort to chart the entire seafloor in Australian waters by 2030.
The data feeds into a live stream in the control room, as undiscovered peaks, valleys and underwater volcanoes reveal themselves in rainbow-coloured hues.
In a month, the Investigator will swing back into Sydney Harbour before returning home to Hobart – hopefully with groundbreaking data about a force that shapes Australia’s weather, environment and food security in tow.
“We range from different types of science – oceanographic, biological, geoscience – all the way from the equator down to the Antarctic sea ice,” voyage manager Margot Hind says with her boots planted on the Investigator’s bridge.
“This is pretty unique in that their study area is so close to port. They’ll head on out and they’ll be getting stuck right into the science.”
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