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Tropical basin interactions and the climatic linkages between mid-to-high latitudes and the tropics are active research areas. These interactions include the influence of El Niño-Southern Oscillation (ENSO) on the tropical Indian and Atlantic oceans, the feedback from these basins on ENSO, the influence of the tropics on mid-to-high-latitude climates, and the feedback from higher latitudes on tropical climate variability. This review summarizes the current understanding of these relationships and key underlying physical processes. In particular, we assessed the current knowledge of tropical variability and the interactions between the tropics and extratropics, including ENSO variability and diversity, the influence of ENSO on the tropical Atlantic and Indian Oceans, interactions among tropical basins on different timescales, variability in the Atlantic meridional overturning circulation (AMOC), the effect of tropical basins on the AMOC, the relationship between the AMOC and Atlantic multidecadal variability, the influence of the AMOC on ENSO and tropical variability, and the impact of other mid-to-high-latitude processes on tropical variability. Although ENSO is the dominant mode of variability on interannual timescales, its characteristics are not stationary and can be influenced by processes from other tropical basins and mid-to-high latitudes. The strength and variations of these interactions among different tropical basins and latitudes can be modulated by changes in external forcing, whether of natural or anthropogenic origin, and may also be shaped by nonlinear interactions between different modes of internal variability.

Surface hydrology in the tropical eastern Indian Ocean significantly impacts low-latitude climate processes including the Indonesian-Australian Monsoon and the Indian Ocean Dipole. Deciphering the evolution of surface hydrology and driving mechanisms is thus important to better understand low-latitude and global climate change. Here, we present ~206 yr-resolved temperature and salinity records of surface waters spanning the past ~31 kyr, based on δ18O and Mg/Ca ratio of Globigerinoides ruber from Core SO18567 retrieved offshore northwestern Australia in the tropical eastern Indian Ocean. By integrating new records with published paleo-oceanographic and -climatological records, we found that increasing sea surface temperature and decreasing salinity in the tropical eastern Indian Ocean during the Heinrich stadial 1 and the Younger Dryas could be attributed to collapse of the Atlantic Meridional Overturning Circulation (AMOC). Melting of Northern Hemisphere ice sheets would have led to a southward shift of the Intertropical Convergence Zone (ITCZ) and reduced transport of warm surface waters from the low latitudes to the Northern Hemisphere high latitudes. In addition, our results indicate that the onset of the last deglacial warming in low latitudes was linked to weakening of the Hadley circulation and AMOC due to warming of Northern Hemisphere high latitudes, rather than raised global atmospheric CO2 concentration.