Tree-ring cellulose δ18O records similar large-scale climate influences as precipitation δ18O in the Northwest Territories of Canada

Oxygen stable isotopes measured in tree rings have been useful for reconstructing climate variability and explaining changes in physiological processes occurring in forests, complementing other more widely studied tree-ring parameters such as ring width. Here, we analyzed the relationships between different climate parameters and annually resolved tree-ring δ18O records (d18OTR) from white spruce (Picea glauca [Moench]Voss) trees located near Tungsten, Northwest Territories, Canada, and used the NASA GISS ModelE2 isotopically equipped general circulation model (GCM) to interpret the relationships in an idealized sense. The d18OTR series were primarily related to temperature variations in spring and summer, likely through temperature effects on the precipitation δ18O with a combination of evaporative enrichment at leaf level in summer. The GCM simulations showed significant positive relationships between modelled precipitation δ18O over the study region and surface temperature and geopotential height over northwestern North America, with stronger patterns during fall winter than during spring-summer. The modelled precipitation δ18O was only significantly associated with moisture transport during the fall-winter season. The d18OTR showed similar correlation patterns to modelled precipitation δ18O during spring-summer, with significant positive correlations with surface temperature and geopotential height, but no correlations with moisture transport. Overall, the d18OTR records for northwestern Canada reflect the same significant large-scale climate patterns as precipitation δ18O for spring-summer, and therefore have potential for reconstructions past atmospheric dynamics in addition to temperature variability.