Doctoral Dissertation Research: Holocene Fluvial Response to Environmental Change in the Uinta Mountains of Northeastern Utah

全新世（冰期后）时期气候变化与北美洪水之间关系的长期年表主要局限于密西西比河上游河谷和美国西南部。这些地区提供了有价值的见解，但其他地区和整个大陆的冰川后物理系统动力学动力学仍然不完整。这个博士论文研究项目将集中在径流和洪水对气候变化的响应，记录在犹他州北部尤塔山脉北坡的遗存河流系统。该地区低梯度河流经历了广泛的横向迁移，原有河道被保留为废弃的曲流。通过将水力方程应用于遗留河道的测量尺寸，定量地重建过去淹没这些河道的洪水的震级。填充物沉积物将沿着垂直于每个遗留河道的样条使用岩心进行分析。每个遗留河道的模态洪水震级将与同一地点的现代模态洪水震级进行比较，并根据相关流域面积进行校准。通过对河道填充物中的有机物进行放射性碳定年，可以直接确定遗留河道的绝对年龄。这些分析的结果将用于重建犹他州北部半干旱地区冰川后洪水的年表。预计过去洪水的结果将有助于更好地了解未来气候变化如何影响同一地区的径流和洪水。这些结果还应该为测试预测区域水文对大陆尺度大气环流模式变化的响应的模型提供证据。尤塔研究区特别适合研究气候变化与洪水行为之间的联系，因为该地区位于大尺度大气环流边界。大尺度半球环流模式的变化，例如与厄尔尼诺/南方涛动有关的变化，已被证明影响融雪洪水的强度。这些遗留河道过去的洪水记录将用于评估洪水制度对气候变化的敏感性，并将与其他地区过去洪水的长期年表进行比较，以评估全新世半球环流模式的行为。地层记录中记录的水文反应也将加强对影响科罗拉多河流域供水的动力学的理解，因为该盆地的夏季水生产是由尤因塔山脉和周围山脉的径流维持的。此外，研究区位于干旱的西南地区和湿润的中西部地区之间的过渡位置，为理解气候变化与水文响应之间的大陆尺度联系提供了一个框架。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Long-term chronologies of relations between climate change and floods in North America during the Holocene (post-glacial) epoch primarily are restricted to the Upper Mississippi Valley and American Southwest. These areas provide valuable insights, but the dynamics of post-glacial physical system dynamics in other locales and for the continent as a whole remain incomplete. This doctoral dissertation research project will focus on the responses of runoff and floods to climate change recorded in relict river systems along the north slope of the Uinta Mountains in northern Utah. Low-gradient streams in this region have experienced extensive lateral migration, with former channels preserved as abandoned meanders. The magnitudes of past floods that filled these channels will be quantitatively reconstructed by applying hydraulic equations to the surveyed dimensions of relict channels. Fill sediments will be analyzed using drill cores along transects perpendicular to each relict channel. The magnitude of the modal flood for each relict channel will be compared with the magnitude of the modern modal flood at the same location and calibrated for the associated drainage basin area. Absolute ages of relict channels will be constrained directly through the use of radiocarbon dating on organic material in the channel fills. The results of these analyses will be used to reconstruct a chronology of post-glacial floods in this semi-arid region of northern Utah. The results of past flooding are expected to contribute to improved understanding of how future climate changes might influence runoff and flooding in this same region. The results also should provide evidence to test models that predict regional hydrologic responses to continental-scale changes in atmospheric circulation patterns. The Uinta study area is particularly appropriate for examination of linkages between climate change and flooding behavior because the region lies along a large-scale atmospheric circulation boundary. Variability in large-scale hemispheric circulation patterns, such as those associated with El Nino/Southern Oscillation, has been shown to influence the magnitude of the snowmelt floods. The records of past floods from these relict channels will be used to evaluate sensitivity of flood regimes to climate changes and will be compared to long-term chronologies of past floods from other regions to assess the behavior of hemispheric circulation patterns through the Holocene. The hydrologic responses recorded in the stratigraphic record also will enhance understandings of the dynamics affecting water supply in the Colorado River basin, because summer water production in this basin is sustained by runoff from the Uintas and surrounding ranges. Furthermore, the study area's transitional location between locations of similar prior studies in the arid Southwest and the humid Midwest provides a framework for understanding continental-scale linkages between climate change and hydrological responses. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.