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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2017-63
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
16 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
A Study of the Variability of the Benguela Current
Sudip Majumder1 and Claudia Schmid2 1Cooperative Institute for Marine and Atmospheric Studies, University of Miami, Miami, Florida, USA
2Atlantic Oceanographic and Meteorological Laboratory, NO AA, Miami, Florida, USA
Abstract. The Benguela Current forms the eastern limb of the subtropical gyre in the South Atlantic and transports a blend of relatively fresh and cool Atlantic water as well as relatively warm and salty Indian Ocean water northward. Therefore, it plays an important role not only for the local freshwater and heat budgets but for the overall meridional heat and freshwater transports in the South Atlantic. Historically, the Benguela Current region is relatively data sparse, especially with respect to long-term observations. A new three dimensional data set of the horizontal velocity in the upper 2000 m that covers the years 1993 to 2015 is used to analyze the variability of the Benguela Current. This data set was derived using observations from Argo floats, satellite sea surface height and wind fields. The main features of the horizontal circulation observed in this data set are in good agreement with those from earlier observations based on more limited data sets. Therefore, it can be used for a more detailed study the flow pattern as well as the variability of the circulation in this region. It is found that the mean meridional transport in the upper 800 m between the continental shelf of Africa and 3° E, decreases from 23 ± 3 Sv at 31° S to 11 ± 3 Sv at 28° S.

In terms of variability, the 23-year long timeseries at 30° S and 35° S reveal phases with large energy densities at periods of 3 to 7 months, which can be attributed to the occurrence of Agulhas rings in this region. The prevalence of these rings is also behind the fact that the energy density at 35° S at the annual period is smaller than at 30° S, because the former latitude is closer to Agulhas retroflection and therefore more likely to be impacted by the Agulhas rings. In agreement with this, the energy density associated with mesoscale variability at 30° S is weaker than at 35° S. With respect to the forcing, the significant correlation between the Sverdrup balance derived from the wind stress and the observed transports at 30° S is 0.7. No significant correlation between these parameters was found at 35° S.


Citation: Majumder, S. and Schmid, C.: A Study of the Variability of the Benguela Current, Ocean Sci. Discuss., https://doi.org/10.5194/os-2017-63, in review, 2017.
Sudip Majumder and Claudia Schmid
Sudip Majumder and Claudia Schmid
Sudip Majumder and Claudia Schmid

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Short summary
A new three dimensional data set of the horizontal velocity in the upper 2000 m that covers the years 1993 to 2015 is used to analyze the variability of the Benguela Current. This data set was derived using observations from Argo floats, satellite sea surface height and wind fields. With this new observational data set we identify the complex flow pattern in this region and provide a detailed analysis of the variability of the volume transport of this current.
A new three dimensional data set of the horizontal velocity in the upper 2000 m that covers the...
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