The Indian Ocean is unique and different to other tropical ocean basins. Yet, our understanding of its variability and perceived influence on regional and global climate has been limited. Due to the presence of the Asian continent, the Indian Ocean features seasonally reversing winds and ocean currents, as well as a lack of northward heat export. The lack of steady easterly winds, combined with a low-latitude connection to the Pacific Ocean, result in a relatively deep thermocline along the equator. These characteristics shape the Indian Ocean’s air-sea interactions, as well as its variability on (intra)seasonal, interannual, and decadal timescales. These features also make the basin and its surrounding regions – home to more than a third of the world’s population – particularly vulnerable to anthropogenic climate change.

The Indian Ocean Dipole as the basin’s leading mode of variability was only first formally described in 1999; twenty years on, the Indian Ocean has evolved from being termed “oceanographers’ stepchild” to a headline grabbing climate driver. The record Indian Ocean Dipole event of 2019 is currently coming to an end; and again, as during the last major dipole event in 1997, extreme climatic conditions could be observed in surrounding countries. In the last twenty years, our knowledge about the Indian Ocean’s influence on regional and global climate across a range of timescales has grown considerably, as will be summarised in this talk. Significant trends in heat transport and freshwater fluxes have been recorded in recent decades in the Indian Ocean and the Maritime Continent region. Implications of the observed low-frequency changes for interannual variability in the Indian Ocean and extreme events across the region, including hydroclimatic extremes in surrounding countries, will be discussed. Furthermore, an outlook highlighting continued challenges for Indian Ocean research will be provided.