The Coastal Ocean Off the East Coast of South Africa

Schumann, E. H.

doi:10.1080/00359198709520125

Cited by 65 publications

(40 citation statements)

References 22 publications

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“…The upwelled water domes up over the shelf break and frequently breaks the surface along the inshore boundary of the Agulhas Current (Lutjeharms et al, 2000). This shelf-edge upwelling is found close to the coast near Mbashe, north of East London, but lies further offshore towards the south as the shelf-edge and Agulhas Current begin to diverge from the coast (Schumann, 1987).…”

Section: Introductionmentioning

confidence: 98%

“…The dynamic requirement that vertical current shear requires a horizontal density gradient (the so-called 'thermal wind' equation) means that isotherms slope upwards on the inner boundary of the Current. Cold water is also forced upwards in the bottom boundary layer through the process of Ekman veering (Schumann, 1986;1987), while divergence of isobaths as the shelf widens southwards of Port Alfred will contribute to this upwelling (Gill and Schumann, 1979).…”

Section: Introductionmentioning

confidence: 99%

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Coastal upwelling on the far eastern Agulhas Bank associated with large meanders in the Agulhas Current

Goschen

Bornman

Deyzel

et al. 2015

Continental Shelf Research

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a b s t r a c tSix large solitary meanders in the Agulhas Current, so-called Natal Pulses, propagated down the eastern coast of South Africa between 2009 and 2011. Their influence on the coastal waters between Port Alfred and Algoa Bay, on the far eastern Agulhas Bank, was measured by thermistor strings moored at 30-80 m bottom depths and two current metres (30 m bottom depth) located at both sides of Algoa Bay. During all events active upwelling lasting 1-3 weeks was observed over the inner shelf and in Algoa Bay. During upwelling the isotherms ascended at an average rate of 1.8 m day À 1 as the cold bottom layer increased in thickness to 40-60 m, although upwelled water did not break the surface in all cases. Cold water remained in the area for a further 2-3 weeks. During three Natal Pulses the water temperatures at the outer moorings initially increased as the plume of the leading edge (crest) of the meander moved onshore. During one Natal Pulse upwelling was recorded before the warm water plume impacted the moorings. At the onset of upwelling currents switched to the southwest in the case of Bird Island and southward at the Cape Recife inner-bay site and reached a maximum speed of 80 cm s À 1 . During all Natal Pulses cold bottom water (10-12°C) flooded over the 80 m bottom depth moorings as the crest of the meander moved onshore, but also around the same time the core of the Agulhas Current began to move offshore. In all cases upwelling was wide-spread.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Coastal upwelling on the far eastern Agulhas Bank associated with large meanders in the Agulhas Current

Goschen

Bornman

Deyzel

et al. 2015

Continental Shelf Research

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“…The continental shelf at Port Alfred is very narrow and steep, and the Agulhas Current flows closer inshore there than at sites to the west of Port Elizabeth. Consequently, this site experiences greater exposure to the current, which reaches southwesterly velocities of 100 to 300 cm s -1 (Schumann 1987, Schumann et al 1991, Boyd et al 1992, Boyd & Shillington 1994. Larvae that hatch at Port Alfred are thus more likely to be swept into the core of the Current, thereafter being transported rapidly offshore and to the southwest.…”

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confidence: 99%

Long-distance migration of South African deep-water rock lobster Palinurus gilchristi

Groeneveld¹,

Branch²

2002

Mar. Ecol. Prog. Ser.

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Long-term movement patterns of deep-water rock lobster Palinurus gilchristi were investigated off the south coast of South Africa using tag recapture data. Over a 12 yr period (1988 to 1999), 30 043 lobsters were tagged at 5 sites. From west to east, these were Cape Agulhas, West and East Agulhas Bank, Mossel Bay to Port Elizabeth, and Port Alfred. The overall recapture rate was 7.51%, with individuals remaining at large for up to 10.3 yr. Overall, 547 (25.8%) tagged lobsters of both sexes moved > 20 km within or between sites. We hypothesized that counter-current migration of juveniles would occur to redress downstream dispersal of phyllosoma larvae by the westerly flowing Agulhas Current. The vast majority of migrants (72.6%) did prove to be immature (carapace length < 72 mm) and did migrate eastwards against the prevailing flow of the Agulhas Current. The Cape Agulhas population (at the western extreme) comprised juveniles only. Over 97% migrated > 50 km, either southeastwards offshore to the West and East Agulhas Bank sites (106 lobsters, covering a mean distance of 154 km), or eastwards alongshore to the Mossel Bay to Port Elizabeth site near the center of the range (33 lobsters, 461 km). The fastest 5% of migrants moved at 0.43 to 0.78 km d -1

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“…The south coast is characterized by distinct physical and hydrodynamic features (Schumann, 1987). It is distinguished by the southwest flowing warm Agulhas current, and physically bounded by a wider shelf down to 200 m isobath with the edge of the shelf dropping steeply and narrowing towards the east (Fig.…”

Section: Data Sourcementioning

confidence: 99%

Indicators of change in the size structure of fish communities: A case study from the south coast of South Africa

Yemane

Field

Leslie³

2008

Fisheries Research

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The Coastal Ocean Off the East Coast of South Africa

Cited by 65 publications

References 22 publications

Coastal upwelling on the far eastern Agulhas Bank associated with large meanders in the Agulhas Current

Coastal upwelling on the far eastern Agulhas Bank associated with large meanders in the Agulhas Current

Long-distance migration of South African deep-water rock lobster Palinurus gilchristi

Indicators of change in the size structure of fish communities: A case study from the south coast of South Africa

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