Large- and mesoscale features of the Angola-Benguela front

Large- and mesoscale features of the frontal system which separates the waters of the Benguela and Angola systems are described. Although salinity data suggest that the front may extend to a depth of at least 200 m, it is particularly marked in the upper 50 m where it can be defined in terms of both temperature and salinity. A horizontal sea surface temperature (SST) gradient of 4°C per 1° of latitude is typical near the coast, and the position of the zone of maximum gradient varies seasonally between, on average, 15 and 17°S, i.e. off southern Angola. The front corresponds to the convergence zone between the north-moving surface waters of the Benguela (modified Central Water) and the south-flowing Angola Current, which is of mixed tropical/equatorial origin and, as such, marks the northern boundary of the Benguela and the southern boundary of the intense shallow thermocline which is a permanent feature off Angola. An analysis of many observations by season shows that mesoscale poleward-directed tongue-li...