A prize example of this interrelatedness and complexity is el ni o, an episodic atmospheric and oceanic phenomenon of the equatorial pacific ocean, particularly prominent along the west coast of south america. Abnormally warm water appears at the surface of the ocean off the west coast of south. America, replacing the cold, nutrient-rich water that usually prevails. thought to be a local phenomenon. El ni o is associated with changes in pressure, wind, precipitation, and ocean conditions over large regions of earth. Every three to seven years, however, the warming of the ocean is much greater, and fishing is likely to be much poorer. Normal pattern usually the waters off the west coast of south america are cool. Wind and pressure patterns in this region are dominated by the persistent subtropical. High (sth) associated with the subsiding air of the hadley cell circulation. As the trade winds diverge from the sth, they flow from east to west across the.