College of Agriculture, Engineering
and Science (CAES)

Ocean Turbulence Under the Spotlight at Workshop

UKZN’s Department of Civil Engineering held the first ever workshop on Ocean Turbulence in South Africa.

The workshop was facilitated by Derek Stretch, Professor for Environmental Fluid Mechanics, with funding provided through an Office of Naval Research (ONR) global grant.

Turbulence at microstructure scales (a centimetre or less) is an important mechanism for mixing in the ocean where regions of enhanced turbulence can influence the entire marine food web. Turbulence is, however, difficult to measure and requires very sensitive and specialised equipment and highly skilled scientists to process and interpret the data.

The week-long workshop aimed at advancing South Africa’s expertise and capacity in state-of-the-art ocean measurement techniques and was taught by specialists in microstructure measurements from Rockland Scientific in Canada, Dr Ralf Lueck and Mr Evan Cervelli.

20 scientists, postgraduate students, and technicians from Durban, Cape Town and Stellenbosch attended to learn about the theory of turbulence and practical measurement techniques.

The workshop included sessions on instrument handling and data processing. Participants enjoyed a trip to the Durban Harbour where they measured the turbulence in the water column generated by a large vessel entering the harbour.  They appreciated being able to get hands-on practice with data processing and data visualisation using Matlab.

Following this workshop, a UKZN research team from the environmental fluid mechanics laboratory spent a week in Sodwana Bay measuring small scale turbulence in the Agulhas current, one of the world’s strongest ocean currents. The team included Stretch, Dr Sam Kumarasamy, Dr Justin Pringle, Dr Katrin Tirok, Mr Atish Deoraj, and Mr Chris Muledy and was joined by Cervelli and Lueck from Rockland Scientific who supported the field measurements.

This research project by Stretch running through the same ONR grant investigates turbulence and mixing in the coastal ocean near Sodwana Bay, an area that is linked to the Agulhas system. The highly energetic Agulhas Current provides an ideal opportunity to develop new insights and understanding of the turbulent mixing processes in the area and their role in the functioning of the marine ecosystem. Regions of enhanced turbulence are associated with heightened biological activity with increased densities of zooplankton and mid-level nekton which in turn attract top marine predators. Sodwana Bay is known for enigmatic species like coelacanths, manta rays, and whale sharks.

Words:  Katrin Tirok