Abstract
A coupled numerical hydrodynamic model is presented for the Cape Peninsula region of South Africa. The model is intended to support a range of interdisciplinary coastal management and research applications, given the multifaceted socio-economic and ecological value of the study area. Calibration and validation are presented, with the model reproducing the mean circulation well. Maximum differences between modelled and measured mean surface current speeds and directions of 3.9 × 10−2 m s−1 and 20.7°, respectively, were produced near Cape Town, where current velocities are moderate. At other measurement sites, the model closely reproduces mean surface and near-bed current speeds and directions and outperforms a global model. In simulating sub-daily velocity variability, the model’s skill is moderate, and similar to that of a global model, where comparison is possible. It offers the distinct advantage of producing information where the global model cannot, however. Validation for temperature and salinity is provided, indicating promising performance. The model produces a range of expected dynamical features for the domain including upwelling and vertical current shear. Nuances in circulation patterns are revealed; specifically, the development of rotational flow patterns within False Bay is qualified and an eddy in Table Bay is identified.
Highlights
Surface gravity waves are the dominant forcing driving currents [5,6,23]. This mechanism was explained for a small embayment just north of the study site by Refs. [26,27] and applies to prevailing south-westerly waves striking the coastline along the eastern margins of Table Bay obliquely, thereby establishing a dominant northward current close to the shore [5,23]
African Navy Hydrographic Office (SANHO) and vertical profile current measurements from an Acoustic Doppler Current Profiler (ADCP) for a point in the south-western reaches of Table Bay were obtained from the Transnet National Ports Authority (TNPA)
Water level measurements for Cape Town and Simon’s Town were obtained from the South African Navy Hydrographic Office (SANHO) and vertical profile current measurements from an Acoustic Doppler Current Profiler (ADCP) for a point in the south-western reaches of Table Bay were obtained from the Transnet National Ports
Summary
The Cape Peninsula area, situated along the southwest coast of South Africa, is defined by Table Bay to the north and False Bay to the south (Figure 1). These bays exhibit complex meteorological-oceanographic dynamics as a result of, among other factors, complex orography, bathymetry [1] and coastal orientation, and the meeting and mixing of warm. False Bay is a southward facing embayment defined by Cape Point (the southern point of the Cape Peninsula) in the west and Cape Hangklip in the east. The complex interactions between these dimensions, against a backdrop of dynamic, storm prone environmental forcing and climate change, make robust coastal management important [11,17]
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