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

气候变化与北美全新世(冰期后)洪水之间关系的长期年表主要局限于密西西比河谷上游和美国西南部。这些领域提供了有价值的见解，但其他地区和整个非洲大陆冰川后物理系统动力学的动态仍然不完整。这项博士论文研究项目将集中在犹他州北部Uinta山脉北坡残留河流系统中记录的径流和洪水对气候变化的响应。该地区的低坡度河流经历了广泛的横向迁移，以前的河道被保留下来，成为废弃的曲流河。通过将水力方程应用于残存河道的测量尺寸，将定量重建填满这些河道的过去洪水的规模。将使用沿垂直于每个残留河道的横断面的钻芯来分析填充沉积物。将每条残留河道的模型洪水等级与相同位置的现代模型洪水等级进行比较，并针对相关的流域区域进行校准。残留河道的绝对年龄将直接通过对河道填充物中的有机材料进行放射性碳测年来限制。这些分析的结果将被用来重建犹他州北部这个半干旱地区的冰川后洪水的年表。过去洪灾的结果预计将有助于更好地了解未来气候变化可能如何影响该地区的径流和洪灾。这一结果还应为预测区域水文响应大陆尺度大气环流模式变化的模型测试提供证据。Uinta研究区特别适合研究气候变化和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沿线。大尺度半球环流模式的可变性，如与厄尔尼诺/南方涛动有关的环流模式，已被证明影响融雪洪水的规模。来自这些残留河道的过去洪水记录将用于评估洪水状况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，以评估整个全新世半球环流模式的行为。地层记录中记录的水文响应还将加强对影响科罗拉多河流域供水的动态的了解，因为该流域夏季的水生产是由乌因塔斯及其周围山脉的径流维持的。此外，研究区位于干旱的西南部和潮湿的中西部的类似先前研究地点之间的过渡位置，为理解气候变化和水文反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.