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South Indian countercurrent and associated fronts

Citation

Menezes, V and Phillips, HE and Schiller, A and Bindoff, NL and Domingues, CM and Vianna, ML, South Indian countercurrent and associated fronts, Journal of Geophysical Research: Oceans, 119, (10) pp. 6763-6791. ISSN 2169-9275 (2014) [Refereed Article]


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Copyright Statement

Copyright 2014 American Geophysical Union

DOI: doi:10.1002/2014JC010076

Abstract

A striking feature of the South Indian Ocean circulation is the presence of the eastward South Indian Countercurrent (SICC) that flows in a direction opposite to that predicted by the classical theories of wind-driven circulation. Several authors suggest that the SICC resembles the subtropical countercurrents (STCCs) observed in other oceans, which are defined as narrow eastward jets on the equatorward side of subtropical gyres, where the depth-integrated flow is westward. These jets are associated with subsurface thermal fronts at thermocline depths by the thermal wind relation. However, the subsurface thermal front associated with the SICC has not been described to date. Other studies conjecture an important role for salinity in controlling the SICC. In the present work, we analyze three Argo-based atlases and data from six hydrographic cruises to investigate whether the SICC is accompanied by permanent thermal and density fronts including salinity effects. The seasonal cycle of these fronts in relation to the SICC strength is also investigated. We find that the SICC is better described as composed of three distinct jets, which we name the northern, central, and southern SICC. We find that the southern SICC around 26S has an associated thermal front at subsurface depths around 100200 m with salinity being of secondary importance. The southern branch strength is related to mode waters poleward of the front, similar to a STCC-like current. However, the SICC multiple jet structure seems to be better described as resulting from PV staircases.

Item Details

Item Type:Refereed Article
Keywords:Indian Ocean, South Indian countercurrent, subtropical Front, vorticity, PV staircase
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Variability (excl. Social Impacts)
Author:Menezes, V (Ms Viviane Menezes)
Author:Phillips, HE (Dr Helen Phillips)
Author:Schiller, A (Dr Andreas Schiller)
Author:Bindoff, NL (Professor Nathan Bindoff)
Author:Domingues, CM (Dr Catia Domingues)
ID Code:94583
Year Published:2014
Funding Support:Australian Research Council (DP130102088)
Web of Science® Times Cited:8
Deposited By:IMAS Research and Education Centre
Deposited On:2014-09-11
Last Modified:2015-04-20
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