The tropical ocean spans 82 percent of Earth’s equatorial circumference (Indonesian maritime continent included). Here, where the atmosphere’s opposing Hadley Cells meet to produce the rainy Intertropical Convergence Zone, the ocean is characterized by a shallow intense thermocline, regional upwelling, and zonally elongated circulation gyres, crisscrossed by Rossby and Kelvin Waves. The tropical ocean draws lots of attention by the climate community as the hot end-member of the global heat engine. There, excess heating is transferred poleward by a variety of coupled oceanic and atmospheric processes, both on the horizontal and vertical planes. Each tropical ocean basin plays a unique role in the climate system because of its particular geography. The Pacific, accounting for about half of the equatorial ocean, hosts the powerful climate presence of El Niño and La Niña, with its near global reach. The Asian Monsoon, imposing strong seasonally reversing meridional winds across the equator, dominates the Indian Ocean. The narrow Atlantic tropics, hemmed in by the jigsaw-puzzle fit of South America and Africa (making a believer in continental drift of a curious school child) holds another special place in Earth’s climate system. While the Atlantic has its own “El Niño” of sorts, and plays a role in the African and American monsoons, its specific attribute is the interhemispheric water exchange across the Atlantic’s tropical belt.