In the Eastern Pacific, there are patterns of interannual, decadal and secular variability associated with environmental change factors such as the El Ni o-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and the Pacific Secular Variability (PSV) defined by the Southern Oscillation Index (SOI), establishing transitory and relatively permanent conditions, determined by the dynamics of the Great Marine Ecosystem of the Humboldt Current (GEMCH), which occupies a large part of the Southeast Pacific. El Ni o is a transcendental event in the oceanic dynamics of the GEMCH, but it is transitory and, after a few months to no more than 2 years, it concludes, returning the system to the conditions of the prevailing decadal moment (periodicity), warm, cold or temperate as differentiated by Euclidean distance analysis. Periodicity is affected by secularity (PSV) defined by the variance of the Southern Oscillation Index. Both periodicity and secularity are climatic states that affect the economies of coastal countries with regionally and globally important fisheries.
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