Benguela Niños and Benguela Niñas in Forced Ocean Simulation From 1958 to 2015

Rodrigue Anicet Imbol Koungue (1) , Mathieu Rouault (2, 3) , Serena Illig (4, 5) , Peter Brandt (6) , Julien Jouanno (4)

1 GEOMAR - Helmholtz Centre for Ocean Research [Kiel]
2 Department of Oceanography [Cape Town]
3 Nansen-Tutu Center for Marine Environmental Research
4 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
5 UCT-OD - Oceanography Department
6 IFM-GEOMAR - Leibniz-Institut für Meereswissenschaften

A systematic study of Benguela Niño and Benguela Niña events during 1958 to 2015 including those that developed before the satellite era (1982) is carried out using an ocean general circulation model in combination with a linear equatorial model. Altogether, 21 strong warm and cold anomalous coastal events are identified among which 6 undocumented extreme coastal events are reported. Results suggest that most of these extreme coastal events including the newly identified ones are linked to remote equatorial forcing via mode 2 equatorial Kelvin waves. The latter propagates after approaching the African coast poleward as coastally trapped waves leading surface temperature anomalies along the Angola‐Benguela current system by one month. One to two months before the peak of Benguela Niños or Niñas usually occurring in March–April, a large‐scale wind stress forcing is observed with both local (variations of alongshore coastal wind stress) and remote forcing developing simultaneously. Results further suggest that surface temperature anomalies off Southern Angola and in the Angola‐Benguela Front are associated with equatorial dynamics and meridional wind stress fluctuations off the southwestern African coast north of 15°S. Similar mechanisms are observed for Northern Namibia in combination with forcing by local meridional wind stress variations.

Domaines: Océan, Atmosphère

Rodrigue Anicet Imbol Koungue, Mathieu Rouault, Serena Illig, Peter Brandt, Julien Jouanno. Benguela Niños and Benguela Niñas in Forced Ocean Simulation From 1958 to 2015. Journal of Geophysical Research. Oceans, 2019, 124 (8), pp.5923-5951. ⟨10.1029/2019JC015013⟩. ⟨ird-04559062⟩