The study, published in the May 19 issue of the journal Nature, holds implications for a diverse body of groups, from scientists who study physical ocean processes such as El Nio events to environmental managers charged with overseeing and sustaining ecosystem resources such as fisheries. Surprisingly, it relates to many disciplines involving complex webs of mutually interacting parts, such as ecosystems and world financial markets, which have the potential for unexpected collapse and irreversible change.
Scripps Professor George Sugihara and Scripps students Chih-hao Hsieh, Sarah Glaser and Andrew Lucas conducted the study--an extension of an advanced graduate course at Scripps--that analyzed the underlying dynamics responsible for major shifts in biological and physical conditions of the North Pacific Ocean over the 20th century.
Scientists hoping to understand the behavior of the North Pacific have centered their analyses on "regime shifts," decades-long changes in which semi-stationary periods are followed by periods of rapid transition. Regimes and rapid shifts between regimes are features that arise from so-called "nonlinear" interactions (where mutual effects do more than add-up, they gang-up and multiply). Nonlinear systems have the capacity for behaviors such as chaos and unpredictable changes of state, changes that can be both dramatic and swift.
The researchers discovered that the data for the North Pacific's biological systems exhibited shift-like fluctuations consistent with "nonlinear" mechanisms. Measuring regimes as distinct from random wiggles in oceanographic time series has been elusive
Contact: Mario Aguilera
University of California - San Diego