A dendroclimatic reconstruction of June–July mean temperature in the northern Canadian Rocky Mountains

A white spruce ring-width chronology was used to reconstruct June–July mean temperatures in the northern Canadian Rocky Mountains back to 1772 A.D. Samples were collected in an old growth subalpine forest in the remote Kwadacha Wilderness Provincial Park. Two chronologies were created, one using standard dendroclimatological methods and one through the use of principal components analysis. The ring-width chronologies both showed a strong positive relationship with minimum, maximum, and mean temperatures during the current growing season. The principal component based chronology was deemed superior for use as a proxy record due to its greater ability to explain the variance in the instrumental temperature record and stronger performance during reconstruction verification. Comparison of this reconstruction with other dendroclimatological reconstructions from western Canada revealed a coherent pattern of low-frequency variability, whereas comparisons at annual times-scales showed considerable temporal and spatial variability in the level of agreement between reconstructions. The northern Canadian Rocky Mountains reconstruction showed no evidence of the reduction in sensitivity to climatic variability that has been found in many other northern spruce chronologies during the late 20th century.