Manifestations of the Pacific Decadal Oscillation shift of 1976 within Alaskan climatology

During 1976, the climatic regime of the Pacific Basin underwent a dramatic shift, as is demonstrated in the switch from a negative to a positive phase in the Pacific Decadal Oscillation (PDO) Index. The climate records of Alaskan first-order stations for the period of ten years previous to 1976 and ten years subsequent to 1976 were examined to determine the specific manner in which the PDO and the resulting circulation shifts affected the weather in Alaska.

Direct comparison of the periods showed that while significant warming of the mean annual temperatures of all of the stations has occurred, the temperature variation on the monthly scale varied widely depending upon region, with the maritime stations showing the most systematic warming, which would be consistent with the greater Pacific Ocean temperatures present in the positive PDO phase. Stations in the Interior and Western regions showed greater variability with some months seeing temperature decreases. The Arctic stations, as expected, displayed the least effect from Pacific influences. Significant decreases in sea-level pressure, indicative of the circulation changes incumbent in the PDO shift, displayed a dramatic effect on temperature increases in the winter months. January temperature increases between the two periods ranged from 2.7°C to 10.7°C. Variation in wind speed, wind direction, and cloudiness also showed significant ties to the regime shift. Examination of the NCEP Reanalysis allows for in-depth study as to the circulation changes that gave rise to the meteorological variation throughout Alaska.

The temperature increases found in the long-term Alaskan time series exhibits cyclic behavior. The sudden temperature increase, which occurred with the 1976 shift, when examined within the context of the long-term time series, displays its great influence upon long-term temperature trends.