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Structure and origin of the subtropical South Indian Ocean Countercurrent
Author(s) -
Siedler Gerold,
Rouault Mathieu,
Lutjeharms Johann R. E.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl027399
Subject(s) - geostrophic wind , geology , hydrography , oceanography , geostrophic current , subtropics , current (fluid) , countercurrent exchange , climatology , physics , biology , fishery , thermodynamics
The structure of the subtropical South Indian Ocean Countercurrent (SICC) is revealed by altimeter‐derived absolute geostrophic surface velocities. It is a narrow, eastward‐flowing current between 22° and 26°S confined to planetary wave trains which propagate westward through the Indian Ocean. Multi‐year averaging identifies it as a well‐defined current between Madagascar and 80°E, continuing with lower intensity between 90° and 100°E. It virtually coincides with the northern limit of Subtropical Underwater subduction. Geostrophic currents from hydrographic sections closely correspond to these surface patterns. Volume transports of the countercurrent down to 800 dbar are of order (10 7 m 3 s −1 ). Evidence is provided for a narrow branch of the South Equatorial Current (SEC) approaching Madagascar near 18°S and feeding the southern East Madagascar Current (EMC) which appears to continue westward around the southern tip of Madagascar. It then partially retroflects and nourishes the SICC.