A climate shift is imminent in the northeast Pacific Ocean, research suggests, and may have a major impact on marine resources, particularly Pacific salmon. Scientists anticipate that the shift, driven by large-scale changes in the Earth's atmospheric wave pattern, will become evident in the next few years. The most recent shift, characterized by a switch from cold and wet conditions to warm and dry conditions in the Pacific northwest of the United States, occurred in 1977 [e.g., Trenberth and Hurell, 1994].
The expected climate shift is suggested by studies of oscillations in ocean surface water drift and in treering records. Drift trajectories, derived from a new measure of decadal variability, showed well-defined oscillations in the 20th century, but researchers were concerned that this decadal nature might not be as evident over a considerably longer time. Thus because of the possible rarity of the 30-year interval since the last climate shift, treering width data was scrutinized for the western juniper for the period from 1500 to 1900 A.D.