Benguela Niños?
What are Benguela Niños?
Every few years, the southeastern tropical Atlantic Ocean is marked by large sea surface temperature (SST) deviations from its seasonal cycle. These deviations are called Benguela Niños, which are extreme and acute events occurring in the Angola-Benguela Area (ABA, 8˚E–20˚E; 20˚S–10˚S, blue box) off the coasts of Angola and Namibia. A Benguela Niño (Niña) is an extreme warm (cold) event, characterized by warmer (colder) sea surface temperatures than normal.
Figure 1. Standard deviation of the monthly mean SST anomalies calculated over the period 1982/01–2022/12. The blue box denotes the Angola-Benguela Area.
Typically, Benguela Niños/Niñas occur in March–April–May (MAM), as shown by the seasonal cycle of the standard deviation of the ABA-averaged SST anomalies (Figure 2). The peak of variability occurs at the end of the warm season (February–March–April). There is a secondary peak of SST variability in November–December, just after the cold season of July–August–September.
Figure 2. Seasonal cycle of the ABA-averaged (a) SST and (b) standard deviation of the SST anomalies using OI-SST over the period 1982–2022.
Plotting a time series of the detrended SST anomalies averaged over the ABA shows the major Benguela Niños/Niñas (Figure 3). We note that since the year 2000, fewer Benguela Niños/Niñas have occurred, as described by Prigent et al. (2020).
Figure 3. Time series of the ABA-averaged detrended OI-SST anomalies. Anomalies were evaluated with respect to the climatology over the period 1982–2022. Red (blue) shades indicate that the SST anomalies are larger (smaller) than one standard deviation (0.73 ˚C).