Using balloons to track ocean currents

The ocean is constantly churning. Vast bodies of water are channelled around the globe, transporting heat, carbon, salt and nutrients like a huge conveyor belt. These ocean currents are of interest to researchers, particularly because they influence (and are influenced by) climate change – but existing technology to monitor intricate and dynamic processes in key regions is prohibitively expensive to deploy.

So a team of University of Southampton scientists and engineers have embarked on a project to design technology that can collect the data at lower cost: by using balloons.

Scientists can use satellite observations to estimate ocean surface circulation at broad scales, but smaller scale processes are difficult to observe. Small, autonomous floats called ‘drifters’ – which literally drift on ocean currents, recording their change in location over time – are deployed to study these regions, but repeated deployment from research ships is costly.

The project proposes an alternative: the balloon-borne drifter. By using a balloon as a means of travel, the device can be launched from land, fly to a target area, and then make a gentle splashdown at a target location, where it will start recording its position as it drifts on ocean currents. The engineers will design components that will allow a balloon to change its altitude so that it can navigate over the ocean using high-altitude winds.

Once developed, the team plan to use computer models to simulate the release of a fleet of drifters over a target region in the ocean: in this case, the Labrador Sea, between Greenland and Canada. “This is an area of particular interest to physical oceanographers and climate scientists, since the Labrador Sea is one site of the headwaters of the meridional overturning circulation,” says co-investigator Dr Eleanor Frajka-Williams, who is an Associate Professor in Physical Oceanography at the University.

“Over recent decades, Greenland has been melting at increasing rates, and while the Arctic has been in a phase of storing freshwater, this could be released and would likely exit the Arctic. We'd like to understand how and why freshwater escapes from the shallow shelves around Greenland, and this new platform will provide an incredible tool towards that end.”

Principal Investigator Dr András Sóbester, who is a Senior Lecturer within Engineering and the Environment at the University, says: "Autonomous systems are set to take an increasing role in observational oceanography. Their success, however, depends on the close alignment of their technological development with the scientific objectives. This multi-disciplinarity is evident in the way we planned FreshWATERS: the computational modelling of ocean currents, the simulations of the balloon flights and the design of the firmware and the hardware are intertwined to deliver a bespoke solution to a challenging observational problem."

The FreshWATERS project, funded by the Natural Environment Research Council (NERC), began earlier this year and will run through to June 2017. Planet Ocean Ltd, a commercial partner, will provide specialist expertise on drifters.