University of Tasmania, Australia

Remarkable near-surface eastward flows in the South Indian Ocean

A remarkable aspect of the upper ocean circulation in the south Indian Ocean (SIO) is the presence of near-surface eastward flows across this basin. Parts of the eastward flow are concentrated into discrete bands and have been identified as the south Indian Countercurrent (SICC) and the Eastern Gyral Current (EGC).  These features have been detected in observations, although details about their precise location, intensity and variability are still to be described.  These currents have been simulated successfully by some numerical models, although their basic dynamics remain unclear.  The most remarkable aspect of the eastward flows is that they are in the opposite direction to that predicted by both Ekman and Sverdrup theory. Recent advances have been made linking Australian and regional climate variability to variability in the Indian Ocean. Before we can further our understanding of the Indian Ocean’s influence on Australian climate, we need to understand the first-order dynamics controlling its circulation and watermass variability.

The study will use observations and high-resolution numerical model output to characterize the spatial and temporal variability of flows in the south Indian Ocean. The student will then use a hierarchy of models, including analytical, linear-continuously-stratified box models and general circulation models, to investigate potential mechanisms for the cause of the eastward flow. The student will join a team that includes UTAS, CSIRO and international researchers