Tree-ring records unveil long-term influence of the Pacific Decadal Oscillation on snowpack dynamics in the Stikine River basin, northern British Columbia

Long hydroclimate records are essential elements for the assessment and management of changing freshwater resources. These records are especially important in transboundary watersheds where international cooperation is required in the joint planning and management process of shared basins. Dendrochronological techniques were used to develop a multicentury record of April 1 snow water equivalent (SWE) for the Stikine River basin in northern British Columbia, Canada, from moisture-sensitive white spruce (Picea glauca) tree rings. Explaining 43% of the instrumental SWE variability, to our knowledge, this research represents the first attempt to develop long-term snowpack reconstructions in northern British Columbia. The results indicated that 15 extreme low April 1 SWE events occurred from 1789 to the beginning of the instrumental record in 1974. The reconstruction record also shows that the occurrence of hydrological extremes in the Stikine River basin is characterized by persistent below-average periods in SWE consistent with phase shifts of the Pacific Decadal Oscillation (PDO). Spectral analyses indicate a very distinct in-phase (positive) relationship between the multidecadal frequencies of variability (similar to 40 years) extracted from the SWE tree-ring reconstruction and other reconstructed winter and spring PDO indices. Comparison of the reconstructed SWE record with other tree-ring-derived PDO proxy records shows coherence at multidecadal frequencies of variability. The research has significant implications for regional watershed management by highlighting the hydrological response of the Stikine River basin to prior climate changes.