Abstract
The Indian Ocean circulation is unlike that of the Pacific and Atlantic Oceans as a result of the basin’s unique geography and patterns established by the seasonally reversing monsoon winds and air-sea exchanges of heat, freshwater, and momentum. The monsoon winds drive seasonally reversing currents north of 10°S. Further south, the winds and currents have a steady direction year-round with weaker seasonal variations in strength and position. While the seasonal average view of the circulation has been understood for some time, expansion of the Indian Ocean observing system and modeling advances have revealed the time-dependent routes of the boundary and interior currents. This chapter discusses the complex connections between the Northern and Southern Hemispheres and between the surface and deep ocean that maintain the basin’s climatological balance of heat and salt, promote upwelling of deep and bottom waters in the global overturning circulation, and provide nutrients to support regional fisheries.