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International Journal of Marine Science 2013, Vol.3, No.34, 267-277
http://ijms.sophiapublisher.com
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stress reaches 0.4 N/m
2
from November to February
(Figure 6a) consistent with accelerated currents
(Figure 6c) and coastal upwelling (1-100m T<12°C,
W>2m/day and S<34.9 g/kg; Figures 6b, d, f
respectively). Vertical uplift (Figure 6d) peaks just
shoreward of the coastal wind and current jet
(17.5-18°E) due to cyclonic vorticity (curl) and
offshore transport (cf. Figure 4a). Warmer, saltier
waters outside the shelf (15-17°E) may incorporate
intrusions of the Agulhas Current in late summer
(Lutjeharms, 2010; Veitch et al., 2010). The coastal T,
S minimum tends to lag winds by 1-2 months,
consistent with SeaWifs chlorophyll reaching furthest
offshore in late summer (Figure 6e). Chlorophyll near
the coast remains above 5 mg m
-3
and peaks from
November to March as in Kone et al (2005). Agenbag
et al (2003) indicate that most fish are caught in the
February-June period.
Figure 6 Mean annual cycle longitude-time plots on 32.5°S (dashed area in Figure 3a) of SODA2.6 a) ECMWF wind stress vectors, b)
1-100 m temperature, c) 1-100m ocean current vectors, d) 1-100 m vertical motion, e) SeaWifs chlorophyll and f) 1-100 m salinity
Note: Time (upward) starts with July. All averaged over the period 1990-2008 except CHL 1998-2010