Tropical ocean conditions and rainfall across the Indian Oceanrealm

We combine numerical model simulations with a network of proxy-based reconstructions of tropical ocean temperature and rainfall over Australasia and Africa, in order to decipher their connection, forcing and feedback mechanisms. Our equilibrium simulations suggest that the upper tropical ocean acts not only as a moisture source but also as an amplifier of relatively small changes in the forcing, thereby regulating the global hydrological cycle. We show that the thermal state in the upper ۲۰۰ m of tropical oceans is more sensitive to insolation gradient, rather than ice volume changes, and is critical for changes in precipitation over East and Southeast Asia on interannual to orbital timescales. On millennial timescales, changes in the vigor of ocean circulation results in a meridional shift in the position of the tropical rainbelt that affects rainfall over South Asia. These changes additionally trigger a zonal dipole pattern across the Indian Ocean that critically influences rainfall over East Africa and Australia/Indonesia.