A CENTURY AND A HALF OF CHANGE IN THE CLIMATE OF THE NE PACIFIC

Spectral analysis of twenty-one climate records indicates that NE Paci fic temperatures and winter wind stress have fluctuated at four domina nt: time scales in this century: 2-3 years (quasi-biennial oscillation ), 5-7 years (El Nino-Southern Oscillation, ENSO), 20-25 years (bideca dal oscillation, BDO), and a poorly resolved, very-low-frequency (VLF) oscillation with a 50-75 year period. Forty-four per cent of the low- frequency variability in British Columbia air temperatures is associat ed with the strength of the Aleutian Low pressure system in winter. On ly 42% of the 'strong' and 25% of the 'moderate' ENSO events in this c entury have produced large warm anomalies off BC. Interactions between the ENSO, bidecadal and very-low-frequency oscillations produce a pat tern of alternating warm and cool climate states, with major warmings every 50 to 75 years. Since 1850 there have been seven warm periods, l asting an average of 11.4 years, and six cool periods lasting an avera ge of 10.8 years. Sharp transitions from cool to warm climate states ( as in 1977/78) occur when warming phases of the BDO and VLF oscillatio ns coincide. Recent evidence suggests that the BDO may originate in ei ther the tropical or the subtropical North Pacific. The NE Pacific has experienced a major warming since 1978. A long-range forecast suggest s that: the BDO and VLF oscillations peaked in 1989 and are currently in a cooling phase. Consequently, coastal temperatures should moderate for the rest of this century. A transition to the next cool climate s tate could occur about the year 2001. The forecast: for moderating tem peratures could begin the first phase of the recovery of the southern BC coastal chinook and coho salmon and herring stocks, which are curre ntly at low abundance levels.