A study of Benguela upwelling system using different upwelling indices derived from remotely sensed data

Two upwelling indices (UI) derived from remotely sensed data, which are related to offshore Ekman transport (UIw) and the Sea Surface Temperature (SST) (UISST), are evaluated to study the spatial and temporal variations of the Benguela Upwelling System (BUS). The comparisons present the advantages and disadvantages of using UISST and UIW to scale upwelling intensity using the chlorophyll-a (Chl-a) concentration as a referential upwelling enhanced relative biomass proxy. The causes for the discrepancies of temporal and spatial variations of UISST, UIW and Chl-a in the BUS area are also discussed. By examining the UISST, UIW and Absolute Dynamic Topography (ADT) at 27–28°S, we find that the extension of the upwelling band is largely impacted by the anti-cyclonic eddy there. Furthermore, we discuss the Benguela Niños in 2006, and estimate the contribution from the wind effects to the total upwelling intensity off Hondeklip and Cape Columbine based on these remote sensing results.