Background:

The Shelf Agulhas Glider Experiment (SAGE) conducted in May 2015 demonstrated the feasibility of operating ocean gliders in the Agulhas Current region. SAGE sparked a lot of interest (see the conversation, sciencemag, and africatimes articles). SAGE allowed us to gain new insight on the impact of the Agulhas Current on the coast and shelf.

Why GINA ? :

Most of our human use of the ocean for fisheries, transportation, and recreation occurs between the open ocean (1500-4000m) and the shallow coastal shelves (50-200m). It is also in these shelf regions that the most intense ocean currents occurs. The ocean currents are key to the transport of mass, heat, salt, biogeochemical variables and plankton (Rudnick, 2016). The Agulhas Current which flows along the south eastern shores of South Africa is the strongest western boundary current of the southern hemisphere and a major driver of variability for the coastal and shelf regions of south-east Africa.

Observing how the Agulhas Current interacts with the coast and shelves is very challenging. This is because changes at the interface between the current and the coast occur over short space and time scales. ocean gliders can help us address some of these observation challenges. Ocean gliders are robotic platforms operated and piloted from land. Sensors on gliders measure such physical variables as pressure, temperature, salinity and current, and biological variables relevant to the abundance of phytoplankton and zooplankton, and also ecologically important chemical variables such as dissolved oxygen, carbon dioxide and nitrate. The data provided by gliders are a natural match for regional models of coastal ocean circulation. The range of parameters measured by gliders also allows for true inter-disciplinary research. This is why ocean gliders are now routinely integrated in global observing systems in many regions of the world.

But while gliders have been successfully operated in the Southern Ocean region since 2012, no sustained glider observations program has been established around the South African’s coastline despite the economic and biological importance of these coastal and shelf regions. GINA is our first step towards a sustained glider observations network around South Africa’s coastline which will complement and enhance existing observing networks such as the Agulhas System Climate Array (ASCA) or Coastal monitoring network managed and maintained by SAEON. The proposed project will serve national development initiatives, such as Operation Phakisa.

Sampling during GINA 2017:

Sampling will take place between June and August 2017.

A map of Sea Surface temperature derived from satellite observations show the warm Agulhas Current closely following the continental shelf break. It is at the interface between the Agulhas Current and the coast that the ocean gliders will flow (white trajectory).

The waveglider will be sampling between the 50m and 500m depth contours (blue lines) while the Seaglider will be sampling between the 300m and 1000m depth contours (red lines).