COASTAL SEA-SURFACE TEMPERATURE VARIABILITY ALONG THE SOUTH COAST OF SOUTH-AFRICA AND THE RELATIONSHIP TO REGIONAL AND GLOBAL CLIMATE

The southern coastline of South Africa is approximately zonal, with a wide (up to 270 ion) shelf region. Intense thermoclines are known to b e established by insolation on the inner shelf region during summer, u pwelling is generated by easterly-component winds, and occasionally Ag ulhas Current water can be advected close to the coast, particularly i n the east. These processes induce daily and seasonal fluctuations of coastal sea-surface temperature (SST), but their influence over longer time scales (interannual) has not yet been tested. Here time series o f SST ranging from 12 to 31 years are examined for inter-relationships with local and regional winds, and the southern oscillation index (SO I). The emphasis is on the summer period, and it is found that the cor relation between SST and major axis wind anomalies can be improved sub stantially by considering the frequency of occurrence of winds above g iven thresholds. Moreover, winds and SSTs are also correlated with the SOI, such that fewer easterly-component winds are experienced at low phases (EI Nino) with consequent increases in coastal SST, and corresp ondingly more easterly-component winds at high phases (La Nina) result in decreased coastal SST; however, these relationships did not hold f or a measuring site within a large open bay area. Long-term trends are also established, with substantial increases in SST (0.25 degrees C/d ecade) in association with greater increases in air temperature (0.36 degrees C/decade).