The work of researchers in UKZN’s Environmental Fluid Mechanics Lab (EFML) on temperature anomalies in the waters around the Sodwana Bay coral reef system and what drives them has been featured in a paper published in the South African Journal of Science and appearing on its cover.
The publication highlights the quality of the research being undertaken and its significance in the context of global climate change.
Titled: Cold Water Temperature Anomalies on the Sodwana Reefs and their Driving Mechanisms, the paper was written by PhD candidate Mr Calvin Wells in partnership with Professor Derek Stretch and Dr Justin Pringle, who together head up the EFML.
Focused on the coral reef system at Sodwana Bay off the KwaZulu-Natal north coast, the study involved an analysis of 21 years of data on temperature changes between 1994 and 2015 on Nine-Mile Reef.
Exposure to elevated temperatures for extended periods, an increasing phenomenon as the climate changes and global sea temperatures rise, causes stress to coral systems and can result in bleaching.
Observing that the Sodwana reef system experiences short-term temperature fluctuations that may provide some relief from bleaching and be crucial to the future survival of the system, the authors set out to understand the mechanisms behind these anomaly events that result in a temperature drop of a few degrees on the reef.
Beginning by exploring the statistical link between these anomalies and the regional hydrodynamics, the trio found that temperature anomalies are not solely driven by the offshore cyclonic eddy interacting with the shelf of the African coastline as previously thought. By examining such an extensive dataset, the EFML team identified additional hydrodynamic patterns that could be significant.
They revealed that the temperature anomalies occur on average three times a year and predominantly during the summer months.
Their examination of the average sea surface heights and regional hydrodynamics over the 21-year period forms part of a larger study into delineating the driving mechanisms of temperature anomalies.
‘The significance of this study cannot be over-emphasised in the context of climate change – a topic of global deliberations in science, policy and development in general,’ said the authors.
Dean and Head of the School of Engineering Professor Glen Bright congratulated the three, saying: ‘This is such excellent work that really places our researchers at the forefront of their fields.’
Wells’ PhD research involves exploring the physics of how reefs function in terms of their interaction with varying flow regimes at micro and macro scales. Extensive field trips to and diving on the Sodwana reef were done to gather hydrodynamic data for analysis.
Field investigations have involved the design and development of a tilt current meter (TCM) to measure currents and temperature just above the reef bottom. The relatively low cost of the meters has allowed the deployment of 20 TCMs around the Sodwana reefs to gather data that will provide insight into the spatial distribution of temperature around the reefs and the associated hydrodynamics.
Wells and fellow PhD student Mr Vibhav Deoraj are also developing numerical models to supplement and explain the interaction between flows and coral reefs – these will unpack the physics of each driving mechanism and the extent to which they influence the cold water temperature anomalies.
By linking these flows and associated turbulent mixing to the temperature and biological functioning of coral reefs, Wells hopes to better understand and define the fundamental role hydrodynamics play in coral reef health.
UKZN’s EFML brings together passionate and motivated researchers whose specialities in fluid mechanics; coastal, ocean and estuarine dynamics, and hydraulic engineering are being applied to enhance the understanding of and provide solutions to several complex environmental issues.
With two PhD and seven master’s students coming through the ranks, the EFML is prioritising innovative research related to developing renewable energy options, improving coastal water quality, predicting the future of shorelines under climate change conditions, and investigating ocean turbulence and the interplay of waves, currents and coral reefs.
Words: Christine Cuénod