El Niño-Southern Oscillation

El Niño-Southern Oscillation (ENSO) is the dominant mode of inter-annual climate variability in the present-day climate system, occurring in the tropical Pacific. It is an oscillation with a period of two to seven years between warm (“El Niño”) and cold (“La Niña”) sea surface temperatures (SSTs) in the eastern tropical pacific, and corresponding changes in surface air pressure known as the Southern Oscillation. This oscillation is caused by interactions between ocean and atmosphere. ENSO has large societal effects: it greatly impacts fishery systems in the eastern tropical Pacific and has an imprint on weather patterns worldwide.
The animation shows the predominate pattern of SST changes in the tropical oceans that are associated with ENSO. Pay attention to the seesaw-like pattern in the Pacific. It is also worth noting that the period of ENSO is irregular, and that not all El Niño and La Niña events are equally strong. Particularly strong El Niño’s occurred in the winters of 1987 and 1997.

Download animated gif file
Download SOS/MP tar file