ENSO
D1. Physical and chemical oceanography and marine meteorologyDefinition
El Nino-Southern Oscillation, the dominant interannual coupled ocean-atmosphere mode in the tropical Pacific.
The El Nino-Southern Oscillation is the dominant year-to-year coupled ocean-atmosphere mode of the tropical Pacific, swinging between warm El Nino and cool La Nina phases roughly every two to seven years. The oceanic side is a basin-wide redistribution of warm water and thermocline depth; the atmospheric side is the Southern Oscillation seesaw in sea-level pressure. Through teleconnections it shifts rainfall, drought, and cyclone patterns worldwide.