Angola–Benguela Front
In comparison to other major oceanic fronts created by the western boundary currents, the ABF is confined to a relatively narrow band of latitudes and is characterized by strong horizontal gradients in sea surface temperature and salinity.
[1] It plays an important role for the southern African continent due to its close proximity to the coast, having a significant impact on the local marine ecosystem and regional climate.
It was Hart and Currie (1960) who first documented the existence of the Angola-Benguela front when the RRS William Scoresby sailed southwards surveying the Benguela Current off the west coast of Africa during the autumn and spring of 1950.
In the early 1970s research increased steadily in this region with subsequent cruises revealing ocean circulation features of the area like the Angola Dome, and began to document the seasonal cycle of the ABF position.
During the past 20 years the cooperation between Angola, Namibia and other countries in Europe and Africa has been greatly improved through different projects and collaborations like the Enhancing Prediction of Tropical Atlantic Climate and its Impacts (PREFACE) (November 2013 - April 2018) and the Benguela Current Commission (BCC).
The objective of these joint research projects has been to investigate and monitor the productivity and oceanographic processes and interactions within the region surrounding the ABF, aiming at improving the management of the fisheries and water resources.
[11] Kostianoy and Lutjeharms (1999) found that short term changes in the ABF are correlated to variations of the pressure gradient driven by the South Atlantic Anticyclone.
In the same study, Colberg and Reason found that the intensity of the ABF is tied to the strength of the meridional wind field which determines the coastal upwelling.
[1][7] Apart from seasonal and mesoscale features, interannual fluctuations of the ABF are also significant and cause great temporal and spatial variability in the frontal zone.
Like the well-known El Niño phenomenon in the South Pacific, these events are characterised by an intense and unusual warming of the surface layer at the coast of Namibia, with positive SST anomalies reaching up to 4 °C.
[3][15][16] During a Benguela Niño, the Angola-Benguela front is abnormally displaced to a southern position, causing a reduced upwelling intensity at the coast and the advection of warm, highly saline water as far as 25°S.
On the one hand, some studies have shown that temperature and upwelling anomalies are caused by local wind changes related to the magnitude and location of South Atlantic Anticyclone.
