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

即将到来的太平洋风暴的轨迹影响了美国西部的降水模式，塑造了干旱和洪水事件。这些轨迹的长期变化可能导致了北美的“巨灾”和其他极端气候事件，但人们对风暴路径模式的变化范围知之甚少，特别是在季节性时间尺度上。降水的同位素组成反映了大气环流模式，记录在树木年轮中。在这项合作研究中，来自北卡罗来纳大学教堂山分校、亚利桑那大学和阿拉斯加大学费尔班克斯分校的研究人员将使用季节性解析的树木年轮数据(基于早材和晚材宽度，18O和13C)和附近地点每周的降水同位素采样，以重建风暴路径的位置和向美国太平洋西北部输送水分的路径。该项目的四个主要目标是：(1)利用树木年轮中的稳定同位素开发风暴路径的长期记录；(2)确定树木年轮中嵌入的季节性信号；(3)检查对太平洋西北地区随时间变化的空间干旱模式的控制；以及(4)评估对未来气候变化的影响。该项目将有助于表征哥伦比亚河流域水分输送系统的稳定性，并对水资源产生影响。考虑到未来气候情景中风暴路径和季节性的预测变化，了解这些系统过去的限制对于评估未来趋势的潜在影响将是重要的。通过该项目产生的数据将扩大整个北美树轮同位素记录的空间复盖面。除了为研究生和本科生提供研究机会外，研究人员还将通过公民-科学合作伙伴关系与太平洋西北地区的教师合作，让初中生和高中生参与数据收集，并加强公立学校的科学教育。

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.