Simulating the Coastal Ocean Circulation Near the Cape Peninsula Using a Coupled Numerical Model

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.

Evaluation of the Population Genetic Structure of Anadara tuberculosa (Mollusca, Bivalvia) in the Panamanian Pacific

“…Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al. 2021 ; Franklin et al. 2025 ).…”

“…Specifically, the Azuero Peninsula separates two oceanographically distinct regions-the Gulf of Chiriquí and the Gulf of Panama-characterized by spatially heterogeneous current and upwelling regimes (D'Croz and O'Dea 2007). Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al 2021;Franklin et al 2025). Consequently, we hypothesized that these complexities might generate mild and localized isolation-most evident between the offshore population of Coiba and the peninsula's southern coast (Isla Cañas)-without necessarily disrupting the broader regional connectivity with populations like Chame.…”

Evaluation of the Population Genetic Structure of Anadara tuberculosa (Mollusca, Bivalvia) in the Panamanian Pacific

“…Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al. 2021 ; Franklin et al. 2025 ).…”

“…Specifically, the Azuero Peninsula separates two oceanographically distinct regions-the Gulf of Chiriquí and the Gulf of Panama-characterized by spatially heterogeneous current and upwelling regimes (D'Croz and O'Dea 2007). Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al 2021;Franklin et al 2025). Consequently, we hypothesized that these complexities might generate mild and localized isolation-most evident between the offshore population of Coiba and the peninsula's southern coast (Isla Cañas)-without necessarily disrupting the broader regional connectivity with populations like Chame.…”

Of Biogeography, Fishes and Kelp: Environmental DNA Metabarcoding the Great African Seaforest

“…One possibility is that eDNA transport across Cape Point has introduced a signal from Benguela-associated taxa into Miller's Point samples. Given the hydrodynamic complexity of Cape Point, where tidal exchange and localised currents can facilitate cross-peninsula transport(De Vos et al 2021), some degree of eDNA mixing between adjacent ecoregions is plausible. This clustering pattern may also indicate that the biogeographical break for fish occurs further east, within False Bay, rather than at Cape Point.…”

Sedimentology of False Bay (Western Cape, South Africa): geological background information for the integrated environmental management of a physically confined coastal compartment

“…Holocene sediments generally produces a cyclonic surface water circulation cell in the bay. As it pushes considerable amounts of water into the bay, the water-level setup along the northern shore frequently causes downwelling, which results in a weak return flow in the opposite direction along the seabed (Morgans 1956;Gründlingh and Largier 1991;Coleman et al 2021;de Vos et al 2021). In this way the water mass in False Bay is continually being overturned during the summer months, thereby supplying oxygenated water even to the deepest parts of the bay, where it supports a rich polychaete fauna in faecalpellet dominated muds (Morgans 1956;Field 1971).…”

Evaluation of the Population Genetic Structure of Anadara tuberculosa (Mollusca, Bivalvia) in the Panamanian Pacific

“…Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al. 2021 ; Franklin et al. 2025 ).…”

“…Specifically, the Azuero Peninsula separates two oceanographically distinct regions-the Gulf of Chiriquí and the Gulf of Panama-characterized by spatially heterogeneous current and upwelling regimes (D'Croz and O'Dea 2007). Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al 2021;Franklin et al 2025). Consequently, we hypothesized that these complexities might generate mild and localized isolation-most evident between the offshore population of Coiba and the peninsula's southern coast (Isla Cañas)-without necessarily disrupting the broader regional connectivity with populations like Chame.…”

Of Biogeography, Fishes and Kelp: Environmental DNA Metabarcoding the Great African Seaforest

“…One possibility is that eDNA transport across Cape Point has introduced a signal from Benguela-associated taxa into Miller's Point samples. Given the hydrodynamic complexity of Cape Point, where tidal exchange and localised currents can facilitate cross-peninsula transport(De Vos et al 2021), some degree of eDNA mixing between adjacent ecoregions is plausible. This clustering pattern may also indicate that the biogeographical break for fish occurs further east, within False Bay, rather than at Cape Point.…”

Sedimentology of False Bay (Western Cape, South Africa): geological background information for the integrated environmental management of a physically confined coastal compartment

“…Holocene sediments generally produces a cyclonic surface water circulation cell in the bay. As it pushes considerable amounts of water into the bay, the water-level setup along the northern shore frequently causes downwelling, which results in a weak return flow in the opposite direction along the seabed (Morgans 1956;Gründlingh and Largier 1991;Coleman et al 2021;de Vos et al 2021). In this way the water mass in False Bay is continually being overturned during the summer months, thereby supplying oxygenated water even to the deepest parts of the bay, where it supports a rich polychaete fauna in faecalpellet dominated muds (Morgans 1956;Field 1971).…”

Evaluation of the Population Genetic Structure of Anadara tuberculosa (Mollusca, Bivalvia) in the Panamanian Pacific

“…Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al. 2021 ; Franklin et al. 2025 ).…”

“…Specifically, the Azuero Peninsula separates two oceanographically distinct regions-the Gulf of Chiriquí and the Gulf of Panama-characterized by spatially heterogeneous current and upwelling regimes (D'Croz and O'Dea 2007). Previous studies suggest that such peninsular geomorphology, combined with wind and tidal patterns, induces hydrodynamic complexities that can alter coastal circulation (de Vos et al 2021;Franklin et al 2025). Consequently, we hypothesized that these complexities might generate mild and localized isolation-most evident between the offshore population of Coiba and the peninsula's southern coast (Isla Cañas)-without necessarily disrupting the broader regional connectivity with populations like Chame.…”

Of Biogeography, Fishes and Kelp: Environmental DNA Metabarcoding the Great African Seaforest

“…One possibility is that eDNA transport across Cape Point has introduced a signal from Benguela-associated taxa into Miller's Point samples. Given the hydrodynamic complexity of Cape Point, where tidal exchange and localised currents can facilitate cross-peninsula transport(De Vos et al 2021), some degree of eDNA mixing between adjacent ecoregions is plausible. This clustering pattern may also indicate that the biogeographical break for fish occurs further east, within False Bay, rather than at Cape Point.…”

Sedimentology of False Bay (Western Cape, South Africa): geological background information for the integrated environmental management of a physically confined coastal compartment

“…Holocene sediments generally produces a cyclonic surface water circulation cell in the bay. As it pushes considerable amounts of water into the bay, the water-level setup along the northern shore frequently causes downwelling, which results in a weak return flow in the opposite direction along the seabed (Morgans 1956;Gründlingh and Largier 1991;Coleman et al 2021;de Vos et al 2021). In this way the water mass in False Bay is continually being overturned during the summer months, thereby supplying oxygenated water even to the deepest parts of the bay, where it supports a rich polychaete fauna in faecalpellet dominated muds (Morgans 1956;Field 1971).…”