Empirical evidence for North Pacific
regime shifts in 1977 and 1989
1 International Pacific Halibut Commission,
P. O. Box 95009, Seattle, WA, 98145-2009.
2 Joint Institute for the Study of the
Atmosphere and Oceans, University of Washington, Box 354235, Seattle, WA
98195-4235
May be cited as: Hare, S. R. and N. J. Mantua.
2000. Empirical evidence for North Pacific regime shifts in 1977
and 1989. Prog. Oceanogr. 47(2-4): 103-146
Abstract
It is now widely accepted that a climatic regime shift transpired in the
North Pacific Ocean in the winter of 1976-77. This regime shift had
far reaching consequences for the large marine ecosystems of the North
Pacific. Despite the strength and scope of the changes initiated
by the regime shift, it was 10-15 years before it was fully recognized.
Subsequent research has suggested that this event was not unique in the
historical record but merely the latest in a succession of climatic regime
shifts. In this study, we assembled 100 environmental time series,
31 climatic and 69 biological, to determine if there is evidence for common
regime signals in the 1965-1997 period of record. Our analysis reproduces
previously documented features of the 1977 regime shift, and identifies
a 1989 shift in some components of the North Pacific ecosystem. The
1989 changes are neither as pervasive as the 1977 changes nor do they signal
a simple return to pre-1977 conditions. A notable feature of the 1989 regime
shift is the relative clarity that is found in biological records, which
contrasts with the relative lack of clear changes expressed by indices
for Pacific climate. Thus, the large marine ecosystems of the North Pacific
and Bering Sea appear to strongly filter climate variability, and respond
nonlinearly to environmental forcing. We conclude that monitoring North
Pacific and Bering Sea ecosystems may allow for an earlier identification
of regime shifts than is possible from monitoring climate data alone.
KEYWORDS: Regime shifts, decadal climate variability, climatic changes,
environmental factors, indicator species, North Pacific
The data used in the analysis (Excel 97) is here
Powerpoint presentation of this paper is here
Copyright © Steven R. Hare
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