Pacific Decadal Oscillation
Many things affect the Northwest's weather. One is the Pacific Decadal Oscillation (PDO). While an El Niño or La Niña typically persists less than 18 months, the PDO lasts 20 to 70 years.
Locations and shifts of cold and warm water in the Pacific alter the path of the jet stream. Changes in the jet stream result in both short and long-term changes in weather patterns.
Recently, unusual atmospheric conditions, not consistent with the PDO or other phenomena, have been observed in the North Pacific, leading some scientists to believe the ocean's part in influencing the weather is still underestimated.
Beyond directly impacting the weather of the Northwest, evidence also suggests that marine ecosystems are influenced by changes in climate. Many questions about these influences remain. In past years, salmon populations have increased off the Pacific Northwest and in Alaska. Under classic PDO scenarios, including during its distinct negative phase from 1947 to 1976, Alaska's stocks would become depleted. This inconsistency may offer more evidence that researchers are still missing several pieces of the climate puzzle.