Environmental Change in the Eastern Tropical Pacific Ocean: Review of ENSO (El Nino/Southern Oscillation) and Decadal Variability

摘要

Interannual variability of the physical environment in the eastern tropical Pacific Ocean (ETP), and biological effects of this variability, are reviewed and compared to variability in the northeastern Pacific. El Nino/Southern Oscillation (ENSO)-scale variability of 2-7 year periods is dominant in the eastern equatorial Pacific and decadal-scale variability of 10-30 year periods is dominant in the northeastern Pacific. In the warm pool at the center of the ETP, temporal variability at any scale is relatively low. ENSO warm (El Nino) and cold (La Nina) events have had a variety of effects on marine populations and ecosystems, but these effects are generally followed by recovery within a few years. El Nino effects such as mortality or reproductive failure are most severe on populations dependent on local feeding or breeding grounds in coastal waters or on islands. Decadal variability has also caused change in populations and ecosystems. Most of these effects have been observed in the California Current, Gulf of Alaska, and other well-studied regions of the Pacific. The 1976-77 phase change or regime shift is the most well-known case of decadal variability.