Watermass characteristics and circulation near 110°E in the southeast Indian Ocean

We present a description of the large-scale physical oceanography of the southeast Indian Ocean to provide context for this special issue, revisiting 110°E as part of the Second International Indian Ocean Expedition. Full watermass properties and circulation are introduced based on the hydrographic observations, as well as underway systems and satellite sea surface height measurements. The 110°E line provides a window into the global meridional overturning circulation and the shallow overturning of the Indian Ocean. Measurements of change along this line provide valuable insight into the pulse of the climate system. The full depth hydrographic transects of 1963 and 2019 will provide invaluable calibration points for investigation of climate variability using the diverse observations that contribute to the Indian and global ocean observing systems.