El Niño–Southern Oscillation (ENSO)

Assembled from 25 blocks · 2 evidence · 19 related

1. Story
2. The largest year-to-year swing in the climate system, and the clearest case of ocean circulation and atmosphere driving each other. In the normal state, trade winds pile warm water in the western Pacific and let cold water rise in the east. When the trades weaken, the warm pool slides east, the thermocline in the eastern Pacific deepens, and coastal upwelling off Peru brings up warm nutrient-poor water instead of cold nutrient-rich water — the anchoveta fishery collapses and rainfall patterns shift across the tropics. NOAA indexes the state by sea surface temperature anomalies in the Niño-3.4 region, 5°N–5°S and 170°W–120°W. As of the Climate Prediction Center discussion of 9 July 2026 an El Niño Advisory was in effect, with El Niño conditions present and forecast to continue.
3. Knowledge
4. Coastal and Equatorial Upwelling
5. El Niño–Southern Oscillation (ENSO)
6. Peruvian Anchoveta (Engraulis ringens)
7. Connections
8. The first global mass bleaching event
9. The second global bleaching event
10. Mass bleaching on the Great Barrier Reef during a La Nina
11. Peruvian Anchoveta (Engraulis ringens)
12. Coastal and Equatorial Upwelling
13. El Niño Advisory in effect at the July 2026 CPC discussion
14. El Niño–Southern Oscillation (ENSO)
15. Coastal and Equatorial Upwelling
16. El Niño Advisory in effect at the July 2026 CPC discussion
17. Humboldt (Peru–Chile) Current
18. Ekman Transport and the Ekman Spiral
19. Thermohaline Circulation
20. El Niño–Southern Oscillation (ENSO)
21. Peruvian Anchoveta (Engraulis ringens)
22. El Niño Advisory in effect at the July 2026 CPC discussion
23. Evidence
24. The ENSO Alert System status at the 9 July 2026 discussion was El Niño Advisory, with El Niño conditions present and forecast to continue; the Niño-3.4 index region is defined as 5°N–5°S, 170°W–120°W. The discussion could not be fetched — the CPC domain is blocked to this run — so no index value or probability is quoted from it.
25. The northern Humboldt Current upwelling system off Peru holds the world's largest single-species fishery, on the Peruvian anchoveta, with fish production per unit area higher than any other region of the world ocean; the wider system has supplied up to about 15 per cent of the global fish catch in some years from roughly 0.1 per cent of the marine surface. Read via search summary alongside Nature Conservancy and IUCN material; not fetched.