Summary of Abstract Submission

Abstract Submission No. IO50-08-0028PresentationPoster

AN OVERVIEW OF THE SOUTH INDIAN OCEAN COUNTERCURRENT: DESCRIBED IN THE SEVENTIES BASED ON IIOE DATA AND REDISCOVERED IN MID-2000

Viviane V. Menezes*1, Helen E. Phillips**1

1 IMAS, University of Tasmania, Australia

ABSTRACT :

The South Indian Ocean circulation is dominated by the presence of near-surface eastward currents flowing between 15S and 30S all the way across the basin from Madagascar to western Australia, in a direction opposite to that predicted by classical theories of wind-driven circulation. What makes these currents unique is that they are generally stronger than their counterparts in the global oceans, deeper and have a peculiar wedge-shaped spatial distribution towards the east, with the thin edge centered at Madagascar and the wide edge at the eastern boundary. Despite their remarkable characteristics, it is only in the late 2000s that they have been described as permanent features of the large-scale circulation, and collectively termed as the South Indian Countercurrent (SICC). However, G. S. Sharma discovered the SICC much earlier using hydrographic data collected during the International Indian Ocean Expedition (IIOE) in the early 1960's. Sharma named the SICC the Tropical Countercurrent, and correctly stated that this current was already evident in all the bimonthly surface geopotential charts from the famous Indian Ocean Atlas produced by Klaus Wyrtki and colleagues in 1971, based mostly on data collected during the IIOE. The present study brings together several pieces of recently published work to give a modern overview of the South Indian Ocean circulation with a focus on the SICC. Based on the analyses of several datasets, we suggest a new schematic diagram for the South Indian Ocean circulation, with objective, dynamically based criteria to label the eastward flows of the South Indian Ocean.