Variability of the Area and Shape of the Benguela Upwelling in 1985–2017 and Its Relation with Dynamic Characteristics from Satellite Measurements

In this paper we study the seasonal and interannual variability of the morphometric characteristics of the Benguela upwelling—shape, area, and length—using satellite measurements of the ocean surface temperature (sear surface temperature (SST)) for 1985–2016. The northern part of the Benguela Upwelling (NBU) (18°–26° S) is characterized by an increase in area from January to July and a minimum in August–December. In the northernmost part of the upwelling (18°–21° S), the largest area is observed in April–August, while it takes on minimal values in January–February and October–November. These changes are associated with the intensification of the southern Angola current, which occurs in February and October, the effect of which can be traced up to 24° S. The maximum in the southern part (28–32°C) of the Benguela upwelling (SBU) is observed for 1–2 months later in May–June, and SBU practically disappears in September–November. In the autumn months, the jet of the northern current of the Agulhas presses against the coast of Africa, contributing to a sharp decrease in the SBU area. On interannual scales, there is a pronounced variability in the upwelling area and the time of its peak. In this case, there is a trend towards an earlier onset of upwelling after 2010. In the northernmost part of the studied area, high values of the upwelling width (150 km) were observed at latitudes of 19°–22° S up to 2000. Then they sharply decrease and the average width decreases almost three times to 50 km. At the same time, there was a sharp increase in the area by the same amount of ~100 km 2 at latitudes 23°–28° S. Thus, there was a sharp change in the upwelling shape, while the total upwelling area remained constant. The weakening and decrease in upwelling in its northernmost part is probably caused by the long-term strengthening of the Angola current, which is observed by altimetry data.