2 86
D. H. CUSIIINO
examined in a later section. The distinctive character of thc Canary
Current region really lies in the shape of the coast, i.e. the entrance to
the Mediterranean and the turii to the eastward of the coastline in the
south ; in detail, the coast is rather indented with prominent capes, with
upwelling taking place to the south of each.
Benguela Current
In the Benguela Current, the upwelling area was described by
Defant (1936) and Hart and Currie (1960) have published a thorough
study of it. They showed a southward seasonal shift and demonstrated
the presence of a countercurrent below about 200 m ; they also described
the " roller bearing " of convergence and divergence about 100 km offshore which corresponds to Sverdrup's dynamic boundary. Buys (1959)
and Darbyshire (1963) have published charts of surface temperature and
have described the system of upwelling. Stander (1964) has studied the
area north of the Orange River and concludes that the most frequent
and intense upwelling occurs between the river and Luderitz about
200 miles north of the Orange River and that as far as Cape Cunene
upwelling in the northern part of South-West Africa decreases northwards. Seasonally, upwelling starts off South-West Africa in midwinter
and continues in the spring. Orren and Shannon (1967) point out that
north of 30"s the upwelling season occurs in spring and early summer,
whereas south of that latitude it takes place in summer and early
autumn. Thus there is a poleward progression of the upwelling from
early spring to early autumn as in other areas. Bang (1971) divides the
upwelling zone into four sections outward from the shore, (1) an inshore
region where the centres of upwelling are, (2) an intermediate zone with
frequent thermal inversions, (3) an offshore divergence belt, (4) and lastly
the oceanic trade-wind drift. There is a belt of slicks running from SSE
to NNW 100 km offshore, which were observed on radar, as strips of
calmness in the surface roughnesses. Jones (1968, 1971) has described
the upwelling system in February 1966 ; he distinguishes between active
and quiescent systems, the latter being characterized by high surface
salinity inshore with low, not high, nutrient levels. So when upwelling
stops, the algal production continues, taking up nutrients, perhaps
without the grazing restraint (because I believe that the grazing
actively restores nutrients to the water due to the destruction of algae).
Figure 11 shows the surface temperature distribution for a 2-year
period between Cap Frio, in South-West Africa and Cap Timiris, north
of Dakar (Berrit, 1961, 1962). The cold water, indicating a seasonal
coastal upwelling, is shown as stippled and shaded areas on the diagram.
There is a seasonal alteration between the Canary Current in the north
D. H. CUSIIINO
examined in a later section. The distinctive character of thc Canary
Current region really lies in the shape of the coast, i.e. the entrance to
the Mediterranean and the turii to the eastward of the coastline in the
south ; in detail, the coast is rather indented with prominent capes, with
upwelling taking place to the south of each.
Benguela Current
In the Benguela Current, the upwelling area was described by
Defant (1936) and Hart and Currie (1960) have published a thorough
study of it. They showed a southward seasonal shift and demonstrated
the presence of a countercurrent below about 200 m ; they also described
the " roller bearing " of convergence and divergence about 100 km offshore which corresponds to Sverdrup's dynamic boundary. Buys (1959)
and Darbyshire (1963) have published charts of surface temperature and
have described the system of upwelling. Stander (1964) has studied the
area north of the Orange River and concludes that the most frequent
and intense upwelling occurs between the river and Luderitz about
200 miles north of the Orange River and that as far as Cape Cunene
upwelling in the northern part of South-West Africa decreases northwards. Seasonally, upwelling starts off South-West Africa in midwinter
and continues in the spring. Orren and Shannon (1967) point out that
north of 30"s the upwelling season occurs in spring and early summer,
whereas south of that latitude it takes place in summer and early
autumn. Thus there is a poleward progression of the upwelling from
early spring to early autumn as in other areas. Bang (1971) divides the
upwelling zone into four sections outward from the shore, (1) an inshore
region where the centres of upwelling are, (2) an intermediate zone with
frequent thermal inversions, (3) an offshore divergence belt, (4) and lastly
the oceanic trade-wind drift. There is a belt of slicks running from SSE
to NNW 100 km offshore, which were observed on radar, as strips of
calmness in the surface roughnesses. Jones (1968, 1971) has described
the upwelling system in February 1966 ; he distinguishes between active
and quiescent systems, the latter being characterized by high surface
salinity inshore with low, not high, nutrient levels. So when upwelling
stops, the algal production continues, taking up nutrients, perhaps
without the grazing restraint (because I believe that the grazing
actively restores nutrients to the water due to the destruction of algae).
Figure 11 shows the surface temperature distribution for a 2-year
period between Cap Frio, in South-West Africa and Cap Timiris, north
of Dakar (Berrit, 1961, 1962). The cold water, indicating a seasonal
coastal upwelling, is shown as stippled and shaded areas on the diagram.
There is a seasonal alteration between the Canary Current in the north