Evidence gleaned from the instrumental record of climate data identifies a robust, recurring pattern of ocean–atmosphere climate variability centered over the midlatitude North Pacific basin. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal timescales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals correspond to dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures, as well as streamflow in major west coast river systems, from Alaska to California.

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*JISAO Contribution Number 379.

+Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, Washington.

#International Pacific Halibut Commission, University of Washington, Seattle, Washington.

@ Fisheries Research Institute, University of Washington, Seattle, Washington.