Thulwaneng sets out to advance coastal modelling in South Africa

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Thulwaneng Mashifane doing nutrient analyses during a research and capacity-building cruise

Thulwaneng Mashifane has joined the SAEON Egagasini Node as a postdoctoral research fellow.

He completed his PhD in Ocean and Atmosphere Science at the University of Cape Town in September 2017.

His thesis investigated biogeochemical interactions in the Benguela upwelling system using in-situ and model data. He used coupled physical-biogeochemical models to understand oceanic production of the greenhouse gas nitrous oxide and implications of nitrogen loss on related cycles in the Benguela.

Results from the models revealed production of nitrous oxide in different water masses in this region. These differences were attributed to remote forcing from the Angola Gyre, a pronounced oxygen minimum zone, and the shallow and deep continental shelf off Walvis Bay and the Angola-Benguela Front respectively.

Nitrogen loss is predominantly through denitrification, coupled with increased phosphate release under low oxygen conditions and a drawdown of silicate to nitrate ratios, resulting in a stoichiometry imbalance in the system. This imbalance could cause a shift in phytoplankton communities with accelerated climate change and a decline in oceanic oxygen content as reported in the South Atlantic.

Thulwaneng’s interest in the Benguela was sparked by participation in several research and capacity-building cruises and observing the dynamic nature of this system. The data collected during the cruises became vital for his PhD study as it was used to evaluate and validate the biogeochemical models. 

Filling knowledge gaps

For his postdoctoral research, Thulwaneng will be focusing on improving representation of biogeochemical cycles in models around the coast of South Africa. A nested configuration zooming in on the St Helena Bay region will be developed for this purpose.

The St Helena Bay region is an important nursery ground for fish. It is also responsible for the main generation of low oxygen water on the coast of South Africa, making it an area of interest for modelling studies. After validation, the configuration can be used to fill knowledge gaps and contribute to the advancement of coastal modelling in South Africa.