The tropical-subtropical coupling in the Southeast Atlantic from the perspective of the northern Benguela upwelling system

PLoS One. 2019 Jan 22;14(1):e0210083. doi: 10.1371/journal.pone.0210083. eCollection 2019.

Abstract

In the Benguela upwelling system, the environmental conditions are determined to a large extent by central water masses advected from remote areas onto the shelf. The origin, spreading pathways and fate of those water masses are investigated with a regional ocean model that is analysed using Eulerian passive tracers and on the basis of Lagrangian trajectories. Two major water masses influencing the Benguela upwelling system are identified: tropical South Atlantic Central Water (SACW) and subtropical Eastern South Atlantic Central Water (ESACW). The spreading of tropical waters into the subtropical Benguela upwelling system is mediated by equatorial currents and their continuation in the Southeast Atlantic. This tropical-subtropical connection has been attributed to signal propagation in the equatorial and coastal waveguides. However, there exists an additional spreading path for tropical central water in the open ocean. This mass transport fluctuates on a seasonal scale around an averaged meridional transport in Sverdrup balance. The inter-annual variability of the advection of tropical waters is related to Benguela Niños, as evidenced by the 2010/2011 event. The northern Benguela upwelling system is a transition zone between SACW and ESACW since they encounter each other at about 20°S. Both water masses have seasonal variable shares in the upwelled water there. To summarise the main pathways of central water mass transport, an enhanced scheme for the subsurface circulation in the Southeast Atlantic is presented.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Atlantic Ocean
  • Environmental Monitoring
  • Seasons*
  • Seawater*
  • Tropical Climate*

Grants and funding

This work was partially funded by the German Federal Ministry of Education and Research within the project Southwest African Coastal Upwelling System and Benguela Niños II (BMBF 03F0751B) and within the project Competence Center for Scalable Data Services and Solutions (ScaDS) Dresden/Leipzig (BMBF 01IS14014B). This work has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 603521. The publication of this article was funded by the Open Access Fund of the Leibniz Association. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.