The strength of the Asian monsoons has been linked to natural oscillations in the Pacific Ocean. When surface temperatures in the eastern equatorial Pacific are warmer than usual (an El Niño event), heavy rains hit East Africa and droughts beset India, Indonesia, and Australia. When ocean conditions flip-flop (a La Niña), so do rainfall patterns across Asia.
The Indian Ocean has its own seesaw behavior, the Indian Ocean Dipole. During a so-called positive phase, warmer-than-usual water temperatures in the western Indian Ocean bring heavy rains to East Africa and India and colder-than-usual waters bring drought to Southeast Asia. In the negative phase, ocean and monsoonal conditions reverse. (Illustration by E. Paul Oberlander, Woods Hole Oceanographic Institution)
MIT/WHOI graduate student Fern Gibbons extracts tiny preserved shells of marine life from sediments cored from the seafloor. The shells hold chemical clues that reveal ocean conditions in the past and suggest how they might change in the future. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)
The seafloor sediments are full of fossilized microscopic shells whose chemistry can reveal ocean temperatures that existed tens of thousands of years ago. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)