Reconstruction of North Pacific Surface Pressure Anomaly Types from Alaskan and Western Candian Tree-ring Data

Spatial anomaly patterns of sea level pressure over the North Pacific sector of the Northern Hemisphere are statistically calibrated with principal components of arctic tree growth. Principal component weights of tree growth prior to 1900 are substituted into the calibration equation to construct the occurrence of past pressure anomaly types in the 19th century. The success of the constructions is statistically tested against independently derived reconstructions of the same pressure anomaly types from a grid of 65 tree-ring sites in western North America and against an independently derived temperature reconstruction for Fairbanks, Alaska. Of the 30 initial regression models developed only two passed enough verification tests against independent data to be considered reasonable reconstructions. The two chosen models were both reconstructing the same pressure anomaly type and were averaged to form a final reconstruction. Climatic conditions inferred from the arctic tree data are an anomalous strengthening of the summer North Pacific High, in the period 1920 to 1940, with associated anomalously cold summer temperatures at Fairbanks summer temperatures as occurred in the early 20th century (1920 to 1938). Based upon this work, recommendations are made for future study.