Moored observations of mesoscale features in the Cape Basin: characteristics and local impacts on water mass distributions

Type Article
Date 2018-09
Language English
Author(s) Kersale Marion1, 2, 3, Lamont Tarron1, 4, Speich Sabrina5, Terre Thierry6, Laxenaire Remi5, Roberts Mike J.4, 7, Van Den Berg Marcel A.4, Ansorge Isabelle J.1
Affiliation(s) 1 : Univ Cape Town, Dept Oceanog, Marine Res Inst, Rondebosch, South Africa.
2 : Univ Miami, Cooperat Inst Marine & Atmospher Studies, Miami, FL 33146 USA.
3 : NOAA, Atlantic Oceanog & Meteorol Lab, Miami, FL 33149 USA.
4 : Oceans & Coastal Res, Dept Environm Affairs, Cape Town, South Africa.
5 : CNRS, ENS, UMR Ecole Polytech 8539, Lab Meteorol Dynam, Paris, France.
6 : Univ Brest, IFREMER, CNRS, IRD,LOPS,IUEM, Plouzane, France.
7 : Nelson Mandela Univ, Ocean Sci & Marine Food Secur, Port Elizabeth, South Africa.
Source Ocean Science (1812-0784) (Copernicus Gesellschaft Mbh), 2018-09 , Vol. 14 , N. 5 , P. 923-945
DOI 10.5194/os-14-923-2018
WOS© Times Cited 10

The eastern side of the South Atlantic Meridional overturning circulation Basin-wide Array (SAMBA) along 34.5 degrees S is used to assess the nonlinear, mesoscale dynamics of the Cape Basin. This array presently consists of current meter moorings and bottom mounted Current and Pressure recording Inverted Echo Sounders (CPIES) 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 mesoscale dynamics on local water mass distribution and cross-validate the different data sets. We demonstrate that the moorings are affected by the complex dynamics of the Cape Basin involving Agulhas rings, cyclonic eddies and anticyclonic eddies from the Agulhas Bank and the South Benguela upwelling front and filaments. 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. These complex dynamics induce strong intra-seasonal upper-ocean velocity variations and water mass exchanges between the shelf and the open ocean but also across the subantarctic and subtropical waters. This work presents the first independent observations comparison between full-depth moorings and CPIES data sets within the eastern South Atlantic region that gives some evidence of eastern boundary buoyancy anomalies associated with migrating eddies. It also high- lights the need to continuously sample the full water depth as inter-basin exchanges occur intermittently and affect the whole water column.

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Kersale Marion, Lamont Tarron, Speich Sabrina, Terre Thierry, Laxenaire Remi, Roberts Mike J., Van Den Berg Marcel A., Ansorge Isabelle J. (2018). Moored observations of mesoscale features in the Cape Basin: characteristics and local impacts on water mass distributions. Ocean Science, 14(5), 923-945. Publisher's official version : , Open Access version :