Authors: Erika Wise*, University of North Carolina at Chapel Hill
Topics: Paleoenvironmental Change, Climatology and Meteorology, Water Resources and Hydrology
Keywords: dendrochronology, dendroclimatology, biogeography, precipitation, atmospheric rivers, climate, tree rings, paleoclimate, runoff, watersheds, extremes
Session Type: Poster
Presentation File: No File Uploaded
Pre-instrumental climate records reconstructed from tree rings have provided crucial context for recent drought and flood events in western North America. Comparisons of these dendroclimate reconstructions with those derived from historical and lake records have identified discrepancies that have been attributed to seasonal biases within the tree-ring data. In general, western North American trees are excellent recorders of moisture during the spring and early summer growing season and the antecedent cool-season, but biological limitations hinder climate capture in the late summer and autumn. While late summer tends to be very dry along the West Coast, atmospheric rivers begin bringing important precipitation to the region in autumn, particularly in the Pacific Northwest. This study examines the role of autumn atmospheric rivers, precipitation, and runoff in selected watersheds, as well as the potential to improve dendroclimatic reconstructions through a focus on this season. Results show that a large portion of autumn precipitation in the Pacific Northwest can be attributed to atmospheric rivers, which peak between September and November in Oregon and Washington. While water-year runoff reconstruction models are more robust on average than season-by-season models, based on traditional model statistics, the seasonal reconstructions are more likely to capture extreme precipitation and runoff years, particularly in basins with a high fraction of precipitation attributable to autumn atmospheric rivers. These results have the potential to more clearly resolve patterns of past moisture delivery over multiple seasons and to support comparisons with other proxy records.