Glider activities bolster South Africa's marine science skill sets

By Jethan d'Hotman, Tamaryn Morris, Juliet Hermes (SAEON)and Marjolaine Krug (CSIR)

Figure 1: Wave glider

Figure 2: Diving glider

Ocean gliders are autonomous remotely operated vehicles that can spend several months at sea collecting data.

The first ever use of gliders off South Africa's east coast was in 2015 as part of the Shelf Agulhas Glider Experiment (SAGE).

During this experiment, two diving gliders were deployed along the ASCA array. The gliders collected valuable data off Algoa Bay, depicting ocean processes occurring at the sub-meso (1–10 km) scale.

As a follow-up, the GINA (Gliders IN the Agulhas) experiment was launched. As part of GINA, a wave glider and a diving glider were deployed off Richards Bay in June 2017 and are collecting data across the continental shelf between Richards Bay and Algoa Bay.

As the name suggests, wave gliders (Figure 1) are able to convert wave energy into forward propulsion to move, while making use of solar energy to power all communications, navigation and other scientific sensors. The wave glider in this experiment is collecting valuable data of sea surface temperature, salinity, dissolved oxygen and carbon fluxes as well as surface currents and winds, while at the same time being able to detect tagged sharks and fish.

Diving gliders (Figure 2) make use of buoyancy to profile the ocean to a maximum depth of 1 000 m. These gliders are able to change their buoyancy and orientation in the water to fly or glide through the ocean to predetermined way points. The diving glider collects subsurface data of temperature, salinity, dissolved oxygen and fluorescence.

Their ability to spend long durations at sea together with the ability to adapt sampling strategies 'on the go', make these platforms an ideal and cost-effective alternative to ship-based observations.

Challenges

Two of the major challenges the gliders face, are the large amount of ship traffic (Figure 3) along South Africa's east coast, and the lack of sunshine over the region at this time of year. Reduced solar energy intake by the wave glider platform has the potential to limit science sampling and, more importantly, communication with the wave glider. SAEON staff and students have received training to help support the team of pilots which looks after the glider on a 24/7 basis.

Figure 3: Ship traffic density map for the East coast of South Africa for 2016 (Courtesy of Marine Traffic)

Capacity building

As part of the GINA experiment, Dr Marjolaine Krug of the Council for Scientific and Industrial Research (CSIR) and Jethan d'Hotman, a Master’s student with SAEON, took part in an international glider training course hosted by the University of Gothenburg in Sweden. The course covered a wide range of topics, including:

Why use gliders and what are they?;
How are gliders deployed and retrieved at sea;
Live piloting and operating gliders;
How gliders sample and experiment design;
Initial data processing;
Conducting quality science using gliders.

Dr Krug was given an opportunity to share her experience from the SAGE project and lessons learnt from operating gliders in such a dynamic and extreme environment as the Agulhas Current. The participants had ample opportunity to interact with glider experts from around the world (Figure 4).

Figure 4: Participants in the international glider training course

A project such as this one can be informative and insightful to both scientists and the public of South Africa. The project offers unique opportunities for capacity development in technical piloting skills and new technologies, bolstering our marine science skill sets.

The GINA experiment has already trained a number of technicians, interns and work-integrated learning students from SAEON in piloting the gliders and we hope to keep the training initiatives ongoing.

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