An evaluation of tree ring records as proxies for historical atmospheric river storm variability in southwest BC

Atmospheric rivers (ARs) influence floods, droughts, and snowpack levels in southwest British Columbia (BC), making their variability consequential to the region's water resources. While instrumental AR data are limited to recent decades, tree ring records can extend knowledge of AR trends by centuries, allowing for better contextualization of current and future AR trends. This research evaluates two dendrochronological methods – tree ring width and tree ring δ18O – for their novel use as proxy records of historical AR variability in southwest BC. Generalized Additive Models reveal that AR data explain tree ring width and δ18O variability not explained by other climate data, suggesting an AR signal. The strength of this signal is stronger for tree ring δ18O, with the percentage of fall precipitation from Pineapple Express (PE)-type ARs explaining up to 44% of δ18O variance. These results indicate the potential for centuries-long PE records and carry important implications for water resource management.