SA ocean gliders tackle climate change

22 October 2013

South African scientists have deployed the first robotics platform in the Southern Ocean in a bid to gauge the precise links between climate and the carbon cycle in the most southern waters of the world’s oceans.

The pioneering project is being led by the marine robotics programme of South Africa’s Council for Scientific and Industrial Research (CSIR), and forms part of the CSIR’s Southern Ocean Carbon Climate Observatory programme.

Announcing the project on Monday, the CSIR said the deployment of the robotics platform over 1 000 kilometres south-west of Cape Town would build on pioneering work from 2012, when the CSIR completed the longest high-resolution missions in the Southern Ocean using five unmanned buoyancy seagliders.

The new robotics platform will combine both wave and buoyancy-driven gliders in an integrated fleet that will undertake a five- to six-month mission to the Antarctic pack-ice and back “at a crucial period, when there are currently no ship-based observations in place”, the CSIR said in a statement.

Understanding ocean-climate links

According to the CSIR’s Ocean Systems and Climate research group leader, Dr Pedro Monteiro, this will be the first global deployment of robotics-based carbon dioxide (CO2) observations in the Southern Ocean, signalling the start of a multi-platform strategy that will hopefully close the uncertainty gap in the global annual CO2 flux estimates within three years.

“These deployments are a great leap towards aiding us in generating a more accurate understanding of the link between climate and the carbon cycle in the ocean,” Monteiro said.

“Combined with global coupled models, this will allow us to understand the intricate relationship of the ocean and atmosphere processes and how these regulate the carbon cycle and ultimately the earth’s climate. It also underlines the important role of the Southern Ocean in global and regional climate.”

The mission coordinator, the CSIR’s Dr Sebastiaan Swart, explained the significance of the dual deployment: “For the first time, we are deploying a wave glider in the Southern Ocean, but of more significance to climate researchers, we have twinned it with a seaglider that dives below the wave glider.

“This will allow us acquire valuable information from both gliders in an integrated approach, but more importantly, this means we can link CO2 flux between the ocean and the atmosphere at the surface of the ocean with understanding of the connected physical and biogeochemical processes that are occurring below the surface and in the ocean interior,” Swart said.

Wave and buoyancy-driven gliders

The deployed liquid robotics wave glider is designed to ride on the ocean surface using the vertical movements of ocean waves to propel it forward. It has specialised instruments on board that measure CO2, the ocean acidity, and other physical variables of the surface ocean. The data generated are sent via satellite communications and viewed in real-time by climate scientists back at the CSIR.

The buoyancy-driven seaglider dives between the surface and a depth of one kilometre. As the glider moves through the water column, it collects valuable data that describe the physics (such as temperature, salinity and the amount of light penetrating into the surface waters) and biogeochemistry (such as phytoplankton and oxygen concentrations of the ocean). These data are transmitted via satellite every time the glider comes back to the surface.

Both gliders are fully controlled by pilots back on land who guide their navigation and activity.

In 2012, the CSIR launched five buoyancy seagliders which were retrieved in February and March this year. According to the CSIR, the data from these gliders are currently being analysed by master’s and doctoral students at the CSIR and the University of Cape Town, with the first scientific papers ready to be submitted for publication in international journals.

Engineering students from the Cape Peninsula University of Technology have also been employed to complete their in-service training and obtain scarce skills from this highly advanced type of marine engineering and robotics technology. This contributes to the CSIR’s HCD goals and skills generation.

“We plan to deploy another set of these gliders in December this year on the SA Agulhas II during its annual voyage to Antarctica so that we can expand our observational coverage,” Swart said.

Monteiro praised the team for its progrees, noting that Swart was working “with some of South Africa’s the best ocean robotics engineers in Derek Needham and Andre Hoek and their new students Sinekhaya Bilana and JP Smit.

“This team is rapidly becoming one of the best-skilled global robotics teams with special experience in Southern Ocean conditions and constraints.”

Funded mainly by the Department of Science and Technology, the Southern Ocean robotics project is being undertaken with local partners Sea Technology Services, the South African Maritime Safety Association and the SA National Antarctic Programme; and with US partners the National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory and the Applied Physics Laboratory at the University of Washington.

SAinfo reporter and the Council for Scientific and Industrial Research