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Benguela current, an Atlantic Niño ?

Lively data, november 30, 2010

The Benguela current is an eastern boundary current, belonging to the South Atlantic subtropical gyre. It flows along the southwestern African coast, from the Cape of Good Hope, moving northwestward  and joining the Angola current. In its southern part, it is characterized by a coastal upwelling with cold-rich waters while in its northern part, it is dominated by warmer tropical waters. 

Time series of Merged Sea Level Anomalies (MSLA in cm) : choose DT - Delayed time Data, DT - Global, (Maps of) Sea Level Anomalies, then Time series(t) in Select view. Click on the map for select the point (here 11°E, 18°S), and finally, select all the time range (1992- March 2010).

Anomalous atmospheric conditions in the western tropical Atlantic (weakening of the South East trade winds off Brazil) can caused the shifting of the Angola-Benguela front further south, causing the intrusion of warm waters. Because of  the similarity to the El Niño phenomenon in the Pacific Ocean (ENSO), this warm event in the South Atlantic Ocean have been named Benguela Niños. These events suppressed the upwelling and caused high rainfall over Namibia. They are less intense and less frequent than ENSO.

One of this event Benguela Niños occurred in 1995. At a given point (11°E/18°S), a long time-serie over all the Delayed-Time period, highlights this positive sea level anomaly : more than 10 cm above normal on March 1995 (austral autumn).

Longitude-time diagram of Sea Level Anomalies (in cm), between 36°W and 15°E, for the latitude 10°S between June 1994 and January 1996. Choose Delayed-time Data, Global, (Maps of) Sea Level Anomalies Merged, the kind of diagram in Select view (longitude-time hofmoeller (xt), the latitude (10°S) and West/East borders. Credits Ssalto/Duacs.

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