NOAA/WDS Paleoclimatology - Eastern United States 325 Year EastNet 2.0 Streamflow Reconstructions

Tree-ring reconstructions of streamflow are uncommon in the eastern United States compared with the western United States. Although the east has not experienced severe drought on the scale of the west over the last 100 years, multiyear droughts have stressed the water management systems throughout the east. Here, we reconstruct mean May-September streamflow of three rivers serving population centers in the northeast (Beaver Kill River serving New York, NY), mid-Atlantic (Potomac River serving Washington, DC), and southeast (Flint River serving Atlanta, GA) to demonstrate the efficacy of reconstructing streamflow in the eastern United States. Then, we conducted an interbasin comparison to identify periods of common variability and examined the influence of the North Atlantic subtropical high on reconstructed streamflow. Our models explained 40-61% of the variance in the instrumental record and passed verification tests in all basins during the period 1675-2000 CE. Droughts and pluvials showed some synchrony across all basins, but the mid-Atlantic region acted as a hinge, sometimes behaving more like the northeast, and other times like the southeast. Climatic analyses suggest a relationship exists between the North Atlantic subtropical high and reconstructed streamflow that influences the probability of drought and pluvial events. Given the many factors influencing tree growth in closed-canopy systems, we have shown that careful standardization of individual tree-ring series, nested regression models, and the use of multiple species can produce robust proxies of streamflow across the eastern seaboard.

与美国西部相比，美国东部基于树木年轮（tree-ring）的径流（streamflow）重建研究较为少见。尽管过去百年间东部未出现与西部规模相当的严重干旱，但持续性干旱已对整个东部地区的水资源管理系统造成显著压力。为此，我们针对服务于东北部、中大西洋地区及东南部人口中心的三座河流——即服务纽约州纽约市的比弗基尔河（Beaver Kill River）、服务华盛顿哥伦比亚特区的波托马克河（Potomac River）以及服务佐治亚州亚特兰大市的弗林特河（Flint River）——重建其5月至9月的平均径流量，以验证在美国东部开展径流重建的有效性。随后，我们开展跨流域对比以识别径流变化的共同时段，并分析了北大西洋副热带高压（North Atlantic subtropical high）对重建径流的影响。我们的模型可解释器测记录中40%至61%的方差，并在1675年至2000年的时段内通过了所有研究流域的验证检验。各流域的干旱与多雨期均存在一定同步性，但中大西洋地区起到了枢纽作用，时而表现得更接近东北部流域，时而又更接近东南部流域。气候分析表明，北大西洋副热带高压与重建径流之间存在显著关联，该关联会影响干旱与多雨事件的发生概率。考虑到郁闭林系统中树木生长受诸多因素影响，本研究证实，对单棵树木年轮序列进行严谨标准化、采用嵌套回归模型以及使用多树种样本，能够在美国东部沿海地区生成可靠的径流代用指标。