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Ocean Science An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
01 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
Moored observations of mesoscale features in the Cape Basin: Characteristics and local impacts on water mass distributions
Marion Kersalé1,2, Tarron Lamont1,3, Sabrina Speich4, Thierry Terre5, Remi Laxenaire4, Mike J. Roberts3,6, Marcel A. van den Berg3, and Isabelle J. Ansorge1 1Marine Research Institute, Department of Oceanography – University of Cape Town, Rondebosch, South Africa
2Cooperative Institute for Marine and Atmospheric Studies, University of Miami, and NOAA/Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida
3Oceans and Coastal Research, Department of Environmental Affairs, South Africa
4Laboratoire de Météorologie Dynamique, UMR 8539 École Polytechnique, ENS, CNRS, Paris, France
5IFREMER, Univ. Brest, CNRS, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM, Plouzané, France
6Ocean Science & Marine Food Security, Nelson Mandela University, Port Elizabeth, South Africa
Abstract. The eastern side of the SAMBA array (South Atlantic Meridional overturning circulation Basin-wide Array) along the latitude 34.5° S is used to assess the nonlinear, mesoscale dynamics of the Cape Basin. This array presently consists of current meter moorings and CPIES (bottom mounted Inverted Echo Sounders with pressure sensor and current meter) deployed across the continental slope. These data, available from September 2014 to December 2015, combined with satellite altimetry allow us to investigate the characteristics and the impact of these mesoscale structures on local water masses distribution and cross-validate the different data sets. We demonstrate that the upper slope moorings are affected by cyclonic eddies generated at the South Benguela upwelling front, while the deeper slope moorings are affected by the more complex dynamics of the Cape Basin involving Agulhas Rings and cyclonic eddies. This complex dynamics induces strong intra-seasonal upper-ocean velocity variations and water masses exchanges across the shelf and the open ocean, but also across the subantarctic and subtropical waters. Under four case studies, the full-water column hydrographic properties of each mesoscale feature has been evaluated. Our analyses show that exchange of water masses happens through the advection of water by mesoscale eddies but also via wide water mass intrusions engendered by the existence of intense dipoles. The high spatial and temporal scales resolved by the moorings allows us to define the substantial role of these mesoscale features over the full-water column. Future investigations with longer time series at these existing sites will lead to a better understanding of the eastern boundary current variability, and ultimately improve our understanding of the strength and variability of the Meridional Overturning Circulation.

Citation: Kersalé, M., Lamont, T., Speich, S., Terre, T., Laxenaire, R., Roberts, M. J., van den Berg, M. A., and Ansorge, I. J.: Moored observations of mesoscale features in the Cape Basin: Characteristics and local impacts on water mass distributions, Ocean Sci. Discuss.,, in review, 2017.
Marion Kersalé et al.
Marion Kersalé et al.
Marion Kersalé et al.


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