05 Dec 2022
05 Dec 2022
Status: this preprint is open for discussion.

Physical processes in the upwelling regions of the tropical Atlantic

Peter Brandt1,2, Gaël Alory3, Founi Mesmin Awo4, Marcus Dengler1, Sandrine Djakouré5, Rodrigue Anicet Imbol Koungue1, Julien Jouanno3, Mareike Körner1, Marisa Roch1, and Mathieu Rouault4 Peter Brandt et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 2Faculty of Mathematics and Natural Sciences, Kiel University, Kiel, Germany
  • 3LEGOS, CNES/CNRS/IRD/UPS, Toulouse, France
  • 4Nansen-Tutu Centre for Marine Environmental Research, Department of Oceanography, University of Cape Town, Cape Town, South Africa
  • 5LASMES, UFR SSMT, Felix Houphouët-Boigny University, Abidjan, Côte d’Ivoire

Abstract. In this paper, we review observational and modelling results on the upwelling in the inner tropical Atlantic. We focus on the physical processes that drive the seasonal variability of surface cooling and upward nutrient flux required to explain the seasonality of primary productivity. We separately consider the equatorial upwelling system, the northern coastal upwelling system of the Gulf of Guinea and the tropical Angolan upwelling system. For the equatorial regime, we discuss the forcing of upwelling velocity and turbulent mixing as well as the underlying dynamics responsible for thermocline movements and current structure. The coastal upwelling system in the Gulf of Guinea is concentrated along northern boundary and is driven by both, local and remote forcing. The particular role of the Guinea Current, nonlinearity and the shape of the coastline are emphasized. For the tropical Angolan upwelling, we show that this system is not wind-driven, but instead results from the combined effect of coastally trapped waves, surface heat and freshwater fluxes, and turbulent mixing. Finally, we review recent changes in the upwelling systems associated with climate variability and global warming and address possible responses of upwelling systems in future scenarios.

Peter Brandt et al.

Status: open (until 21 Feb 2023)

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  • RC1: 'Comment on egusphere-2022-1354', Anonymous Referee #1, 13 Jan 2023 reply

Peter Brandt et al.

Peter Brandt et al.


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Short summary
Tropical upwelling systems are among the most productive ecosystems globally. The tropical Atlantic upwelling undergoes a strong seasonal cycle that is forced by the seasonal cycle of the zonal wind along the equator and the near-coastal wind field off Africa. Besides the wind forcing that lead to an up- and downward movement of the nitracline, turbulent diffusion results in upward mixing of nutrients. Here, we review the different physical processes responsible for upward nutrient supply.