Coastal Ocean Dynamics of the Algoa Bay Region

Investigators: Wayne Goschen, Thomas Bornman, Eckart Schumann
Collaborating Institutions: SAEON Elwandle & Egagasini, Nelson Mandela University Coastal and Marine Research Unit
Email contact: Wayne Goshen


This project aims to investigate the dynamics of the coastal ocean of Algoa Bay and surrounding region over short and long time scales. The physics of the ocean needs to be studied in order to understand how and why the ocean moves (currents) and what constitutes its state, such as its temperature and salinity. Knowledge of these variables, and how they interact, will help in answering certain questions put forward by marine biological investigations that are underway in the region. The project therefore is primarily focused on supporting the biological research, while at the same time gaining knowledge of the physical ocean.

Off Algoa Bay, wind and tides are important drivers of the coastal and shelf waters, while geostrophic and inertial currents are also evident. Further offshore the Agulhas Current flows southwestward along the continental shelf edge (its core about 50 km offshore Algoa Bay) and dominates the ocean processes there. However, warm water intrusions by the upper layers of Agulhas Current frequently penetrate into the shallows of Port Alfred, Algoa Bay and St Francis Bay, as does cold upwelled water driven by the Agulhas Current. During summer, northeasterly winds intensify and wind-driven coastal upwelling off the southern shorelines of the prominent capes are frequent occurrences. This upwelling forms the basis of primary and secondary productivity in the area.

In order to measure these phenomena, underwater temperature recorders, current meters (ADCPs) and gully temperature probes have been deployed at selected locations in the large log-spiral bays of the south and eastern Cape and north towards Port Alfred by SAEON. Automatic weather stations owned by SAWS are operated at in this area and the data is made available to researchers. Tidal data are also accessible through the SA Navy Hydrographic Office while satellite imagery is distributed through UCT Marine Remote Sensing Unit and other web sites. These are useful tools to investigate the physical ocean and will be used in this project.

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