Most coastal mixed layer and upwelling investigations have concentrated on
the more important fisheries regions situated on the west coasts of the con
tinents, while this paper analyzes conditions on the zonally-orientated sou
th coast of South Africa. Most of the data originate from a short measureme
nt program in the southern summer of 1995, involving both CTD measurements
from a small boat and data from a temperature array and coastal sea surface
temperature (SST).
Limited mixed layer statistics are derived and yield results similar to tho
se of Lentz (1992), although a lack of current measurements precludes any a
ssessment of the Ekman drift. It is shown that the nature of the summer win
d forcing is very different to the situation off the South African west coa
st, with wind variability occurring on much shorter time scales from 2 to 6
days: this has important consequences for plankton blooms and is a likely
reason why production is not as efficient off this coast. Past results (Til
ney et al., 1996) have shown the importance of coastal trapped waves at dep
th, but it is apparent that very different conditions occur near the surfac
e.
It is found that the coastal SST is a very good monitor of wind-forced coas
tal upwelling conditions, probably because of the abrupt topography. Substa
ntial baroclinic tidal signals are also apparent at times in the temperatur
e measurements.