P2C2: Detection of Long-term Variability in Storm Tracks Using Seasonally Resolved Tree-ring Isotope Records: Implications for Hydroclimatic Change in the U.S. Pacific Northwest

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The trajectory of incoming storms from the Pacific Ocean influences precipitation patterns in the western United States, shaping drought and flood events. Long-term changes in these trajectories may have resulted in North American "megadroughts" and other extreme climate events, but little is known about the range of variability in storm-track patterns, particularly at a seasonal timescale. The isotopic composition of precipitation, which reflects atmospheric circulation patterns, is recorded in tree rings. In this collaborative study, researchers from the University of North Carolina at Chapel Hill, the University of Arizona, and the University of Alaska, Fairbanks, will use seasonally resolved tree-ring data (based on earlywood and latewood widths, δ18O, and δ13C) and weekly precipitation isotope sampling at nearby sites to reconstruct storm-track position and moisture delivery pathways to the U.S. Pacific Northwest. Four major objectives of this project are to: (1) develop a long-term record of storm track using stable isotopes in tree rings; (2) determine the seasonal signal embedded within the tree rings; (3) examine controls on spatial drought patterns through time in the Pacific Northwest; and (4) evaluate implications for future climate change.This project will help characterize the stability of the moisture-delivery system to the Columbia River Basin, with implications for water resources. Given the projected changes in storm track and seasonality in future climate scenarios, understanding past limits in these systems will be important for evaluating the potential impacts of future trends. Data generated through this project will extend spatial coverage of tree-ring isotope records across North America. In addition to providing research opportunities for graduate and undergraduate students, the researchers will collaborate with teachers in the Pacific Northwest through citizen-science partnerships that will involve middle- and high-school students in data collection and enhance science education in public schools.