Blog icon

On board the RV Investigator, it's perfect glider weather.

Calm seas make launching – or deploying – an autonomous sea glider into the Southern Ocean less of a blast off and more of a splash.

But for oceanographers, today’s high tech autonomous vehicles still bring all the excitement of sending a rocket into space to explore the vast unknown.

We deployed three ocean gliders from our research vessel (RV) Investigator in 2023.

Their work starts around 55 degrees south – about halfway between Tasmania and the Antarctic. Here, the calm surface belies the strength of the water in the Antarctic Circumpolar Current they’ve been sent in to explore.

Voyage into the current

RV Investigator set out from Hobart to investigate why the planet’s strongest current is leaking warm water into the polar seas.

The Antarctic Circumpolar Current acts as a buffer between warm water to the north and the icy continent to the south. It helps keep Antarctica frozen. However, its whirling eddies and finer scale dynamics result in warm water seeping through this barrier towards Antarctica.

The temperatures across the Antarctic Circumpolar Current.

SWOT is revolutionising how scientists observe Earth’s water elevation with 2 kilometres pixel, high-definition, topography. This is 10 times better than previously available.


The gliders were part of an array of monitoring equipment deployed from the ship. Their task was to directly measure the properties of the ocean inside the current. The satellites indirectly measured the height of the ocean surface from space.

Radar information from the satellite is combined with a description of the ocean below the surface over exactly the same location. This allows scientists to create a 3D view of the current.

“I was involved in that satellite preparation 25 years ago. It’s been a very long journey to develop this fantastic new technology.”

Dr Benoit Legresy, CSIRO’s co-chief scientist for the voyage.

Introducing the ocean glider

Sea gliders weigh about 60 kilograms on the dock at dry weight. But once in the water they’re buoyancy neutral and powered by a battery.

Testing and calibrating the gliders before departure.

They move by adjusting buoyancy. Using hydrodynamics and small fins, they can travel up and down the water column up to 1000 metres deep. They can also move against and across the current.

Craig Hanstein is our Technical Officer. He says the buoyancy engine is fundamental to the glider's ability to navigate the currents.

“Everything is set up and measured carefully so it can do those dives. If you don’t get those things right, you will have problems when it’s deployed,” Craig says.

Autonomous underwater gliders are increasingly sophisticated thanks to a payload of finely tuned instruments, or sensors, which measure the water column. These sensors measures things like temperature, salinity, pressure, and dissolved oxygen.

Dr Laura Herraiz Borreguero notes while they’re not new, the gliders are still not common.

“They became commercially available in 2013. Only a very few lucky scientists have actually been able to own or use them,” Laura says.

“A strong constraint on achieving a better understanding of the small-scale ocean processes has been the lack of suitable instruments to resolve the scales at play.”

Two gliders were deployed for the California Institute of Technology (Caltech) and one for CSIRO.

Our glider, which is our first of its kind, is a biogeochemical and physical glider that can collect information about the biology, chemistry and physics of the currents.

Sea gliders can travel up and down through the water column to a depth of 1000m, as well as across the current.

Introducing the pilots

Once deployed, the gliders were not alone. Back in Hobart, the mission control team was led by Laura and Dr Beatriz Peña-Molino.

Bea and Laura were joined by pilots in the United States, on the west coast at Caltech and on the east coast at Brown University. As part of our team, their job was to oversee the gliders 24/7.

“Because of the way the time zones work with the Australia and the US, there's always somebody with eyes on the glider,” Bea says.

Babysitting these highly tuned and expensive pieces of equipment remotely is no small responsibility. Bea’s and Laura’s mobile phones were an ever-present baby monitor over summer, pinging with news from the gliders.

“It was indeed a very busy period and became the first and last thing to do for the day, every day,” Laura says.

Each time it surfaces, a glider establishes communications with the shore station over an Iridium satellite link. The glider then transmits data and receives piloting instructions.

This allows the pilots to monitor progress, check the state of critical systems such as battery level, and make changes to the mission course.

“It requires a lot of thinking and anticipating what the current is doing. We've been working closely with the satellite information, and we change the direction on the glider and try to counteract a little bit what the currents are doing,” Bea says.

“It's like a bit like a kayaker trying to cross a river and thinking, you know, where do I have to start paddling if I want to end up on the opposite side of the river?”

Into the heart of the Antarctic Circumpolar Current

The beauty of the gliders is they can be piloted from shore and sent into the small-scale (10-100km) eddies of the Antarctic Circumpolar Current.

And when the gliders reached the surface to transmit data from the sensors, scientists were truly excited by what they saw.

These gliders had been cruising the polar front profiling the Antarctic Circumpolar Current for four months, transmitting data every four hours.

What’s revolutionary is the scale of data.


Laura describes the sea glider as a “step-changer in ocean observing capabilities”.

“In fact, the data collected has exceeded our expectations!” she says.

Co-pilot Bea says typically, on trips in the Southern Ocean, transects were 100km apart.

"But the glider has been giving us data often every two, three or four kilometres,” Bea says.

“It turns out there's an amazing amount of structure or features in all the properties in between those points. We've seen these beautiful injections of water that normally sit at the surface, all the way down to 700 metres in the ocean. And I'm pretty sure there are no observations of this."

RV Investigator's route as it crosses the polar front, showing changes in temperature.

“The feature in particular I’m thinking of is like a little filament. It's something relatively narrow that you can track from the surface all the way down through time and space into the deep ocean," Bea says.

“We were able to trace one of these events where eddies are able to break these barriers in the current moving the heat southwards. We were super lucky that we were following one of these eddies when it broke off from the current. We made several sections across that eddy as it moved south and it basically was dissipating and releasing all that heat.

“One of the very interesting things that I'm keen to do is to look at how much heat was trapped in this area and then connect it with the satellite data and say, when we observe this at the surface, this is what we see underneath.

“We can then extrapolate this across the circumpolar current and review some of our understanding of how the heat from the subtropical ocean goes south.”


Bringing the glider home

Ocean research is teamwork. Not only did we work with Caltech to deploy their additional gliders, and NASA and CNES on the SWOT satellite, we needed help getting our glider back.

After 3600km – and four months of barnacles hitching a ride – the CSIRO glider had made its way near enough to the path of another RV Investigator voyage to the Southern Ocean.

Technical officer Craig Hanstein wasn’t on board when our glider was deployed, but he was on board for the recovery.

“We coordinated with Laura and Bea. The day we arrived on station to find out where the float was, they could tell the glider via satellite to send a GPS position back to them, which they sent to us. We would go to the office of the watch and sail the ship toward that position,” Craig says.

“We weren’t far away from it and the officer of the watch at the time spotted it.

“The crew on board did a good rescue using the net to capture the sea glider and get it on board safely. In a good 3-4 metre sea swell everything is going up and down and you’ve got to get the net underneath the glider and lift it up at just the right time.”

It was rescued by our voyage chief scientist, Dr Elizabeth Shadwick. Elizabeth was returning from the annual Southern Ocean Time Series voyage to maintain a set of deep-water automated moorings. The moorings form a sub-facility of Australia’s Integrated Marine Observing System (IMOS).

“RV Investigator was close enough that we were able to make a rescue mission possible,” Elizabeth says.

"Really, the success is owed to the captain and the officers and the deck crew who made it look like an easy job of scooping this tiny little thing up in a specialised recovery net we use off the midship coring boom. Really exciting, lots of happy people on board yesterday, or the day before, when we were finally able to get it back.”

Putting the satellite and glider data together

“We were jumping up and down when they finally picked the gliders up, because it’s been a long time,” says Bea.

“The most exciting part for us is this combination with a new satellite technology. Some of the features we’ve seen would have been invisible to us with traditional tools. But with SWOT and the gliders, it’s zoomed into something that we haven’t seen before.

“We’re really excited about putting the data and science in the bigger context and understanding what it means for the Southern Ocean as a whole.”

This research was supported by grants of sea time on RV Investigator from our Marine National Facility. To read more about the science deployed from the FOCUS voyage and highlights from life onboard, go to the voyage blog on our partner’s website Australian Antarctic Program Partnership.


  • Author

    Thea Williams

  • Production editor

    Smriti Daniel

  • Designer

    Aidan Lagats

  • Developer

    Kate Cochrane

  • Images

    CSIRO Archival, Yann-Treden Tranchant (CSIRO), Mark Horstman (Australian Antarctic Program Partnership), Amelia Pearson (Monash University) and Craig Hanstein (CSIRO)

Contact us

Find out how we can help you and your business. Get in touch using the form below and our experts will get in contact soon!

CSIRO will handle your personal information in accordance with the Privacy Act 1988 (Cth) and our Privacy Policy.

First name must be filled in

Surname must be filled in

I am representing *

Please choose an option

Please provide a subject for the enquriy

0 / 100

We'll need to know what you want to contact us about so we can give you an answer

0 / 1900

You shouldn't be able to see this field. Please try again and leave the field blank.