Fig. 1

(a) Geographical location of the Indian Ocean and monsoon-driven currents (modified from Schott et al, 2009), where the red arrows represent currents during summer monsoon, the yellow arrows represent currents during winter monsoon, and the blue and purple arrows represent currents present during both summer and winter; (b) schematic diagram of annual mean sea surface temperature (SST) and the Walker circulation in the modern Warm Pool (modified from Abram et al, 2020)"