Complete Description of the 1998/99 Regime Shift in the North Pacific
Current Status of Accomplishment or Milestone: The study has been completed, and results presented as invited talks at two international scientific conferences, the 10th Annual PICES Meeting, and the 2002 Ocean Sciences Meeting. The results are also being summarized in a manuscript to be submitted to Science, jointly with Bill Peterson (NWFSC).
Background: Fishery populations are known to fluctuate on multidecadal‘cycles’, called regimes, often synchronously with geographically separate stocks. Analyses of physical variables indicates that global-scale variations in climate may be the mechanism responsible for these changes in population size and distribution. Trends in many physical and ecological factors indicate that a major regime shift occurred in the north Pacific in late 1998.
Purpose of Activity/Goal of Project: The project was designed to explain observed changes in fishery populations and ecosystem structure in the northeast Pacific in 1998-99. To do this, we attempted to determine if a climate regime shift indeed occurred at that time and through what possible mechanisms did the observed physical changes impact marine ecosystems.
Description of Accomplishment and Significant Results: A number of atmospheric and oceanic indices changed significantly in late 1998, as did the spatial patterns of several physical parameters. These physical changes were very large and rapid (< 1 year), following a major El Niño in 1997-98. Almost simultaneously, salmon production in the Pacific Northwest increased markedly, and the structure of coastal marine ecosystems, as characterized by the dominant copepod and baitfish species, also changed dramatically. The observed ocean changes suggest a different circulation pattern that may be conducive for a greater biological carrying capacity. At least, it appears that ocean conditions now favor an ecosystem structure that has not been seen since the early 1970s, prior to the previous regime shift.
Significance of Accomplishment (e.g., to the Center, to Management, and to NMFS Strategic plan Goals): Observed long-term changes in the biological community structure and productivity of the north Pacific Ocean may be linked to, and potentially predicted by, climate regime shifts. Evidence suggests that the ecosystem can respond in less than one growing season to a new physical regime and may return rapidly to a former state associated with a previous physical regime. This research indicates that we may be able to characterize ocean regimes in terms of their carrying capacity or suitability for specific stocks.
Problems: None.
Key Contact: Franklin B. Schwing (831-648-9034; Franklin.Schwing@noaa.gov).