Coastal Oceanic climate change and variability from 1982 to 2009 around South Africa
Résumé
We analyze changes and fluctuations in sea surface temperature at the monthly scale around the South African coastline from 1982 to 2009.. There is a statistically significant negative trend of up to 0.55°C per decade in the Southern Benguela from January to August. Cooling trend of lesser magnitude is observed at the South Coast from May to August. This is due to an increase in upwelling favorable southeasterly and easterly wind. Positive trend in sea surface temperature of up to 0.55°C per decade occurred in most part of the Agulhas Current system at all months of the year except for KwaZuluNatal. El Nino Southern Oscillation is significantly positively correlated at the 95 % level with Southern Benguela and South Coast from February to May and negatively correlated with the Agulhas Current system South of 36°S. El Nino suppresses upwelling along the coast while La Nina increases it. Although, there does not seem to be a linear relationship between strength of ENSO and magnitude of coastal SST perturbation, El Nino and La Nina appear to be linked with major warm and cool events at the seasonal scale in late summer in the Southern Benguela and the South Coast. A word of caution is given on low resolution reanalyzed climate data (ERA40 and NCEP) and optimally interpolated Reynolds sea surface temperature used here.
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