Climate Reconstructions (1801 to 1938) Inferred from Tree-Ring Width Chronologies of the North American Arctic

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Abstract
A spatial grid of 56 tree-ring width chronologies from Alaska [USA] and northwestern Canada, from 1801-1938, was reduced using principal components analysis. The principal component weights were calibrated, via multiple regression, against coefficients representing seasonal spatial anomaly patterns of sea-level pressure over the North Pacific sector of the Northern Hemisphere, for the period 1900-1938. The quality of the chosen regression models is determined by statistically testing the models against independent data. The testing data are a temperature reconstruction for Fairbanks and pressue anomaly coefficients derived from western North American tree-ring width chronologies. Climate conditions inferred from the reconstructed pressure-type coefficients were an anomolous strengthening of the summer North Pacific High in the period 1830-1850 and associated anomalously low summer temperatures at Fairbanks. Almost normal summer pressures during the first 15 yr of the 19th century would cause average Fairbanks summer temperatures such as occurred in the early 20th century (1920-1938).