EAR-PF: Revisiting Megafloods: Insights From Glacial Isostatic Adjustment on Flood Size, Flow Routes, and Climate Response

塔玛拉皮科博士已被授予美国国家科学基金会博士后奖学金，以调查冰川均衡调整对晚更新世灾难性洪水的影响，以提高我们对特大洪水的时间和路线的理解。这项工作将在加州理工学院和俄勒冈州州立大学进行。在22,000年至14,000年前的最后一个冰河时代，数十场灾难性的特大洪水从一个冰坝冰川湖米苏拉冲刷了爱达荷州和华盛顿东部的景观，形成了所谓的"疤痕之地"。这些冰川湖爆发是地球上已知的最大洪水。重建这些事件的规模有助于我们了解洪水如何塑造地球景观并与气候突变有关。在洪水期间，冰盖融化导致地壳变形，速率约为10毫米/年，这是区域构造抬升速率以上的数量级，导致区域地形与今天大不相同。冰川均衡调整的这一过程在先前对洪水量或流量的估计中被忽略了，这可能会带来很大的误差，但尚未量化。这项研究将提供洪水事件期间总流量的更准确估计，这反过来将有助于量化海洋和更广泛的气候系统对特大洪水的反应。此外，该研究将通过研究过去灾难性洪水的性质和冰盖对气候变化的稳定性，为突发洪水规划提供信息。PI在科学界妇女和代表性不足的少数群体中具有广泛的领导和外联经验，并将继续致力于参与这些社区。米苏拉湖（Lake Missoula）在22，000年至14，000年前爆发的特大洪水是地球上已知的最大洪水。在这些洪水事件中，先前对水量和流量的估计依赖于基于现代地形的坡度。在这段时间内，冰川均衡调整造成地壳变形率约为10毫米/年，数量级以上的区域隆起率，并改变了约30%的局部坡度。因此，洪水量的先前估计包括一个潜在的大误差，这还没有被量化。此外，在米苏拉洪水的间隔，由于冰川均衡调整的隆起和沉降的模式演变显着，这种地形重塑可以解释观察到的变化，随着时间的推移，洪水路由。该提案，在地貌学和地球物理学的学科，旨在研究冰川均衡调整的影响，在Missoula特大洪水事件的过程中，它开发的delleled Scablands景观。该项目提出了三个相互关联的目标：（1）重建洪水事件间隔期间的排水路径演变，以响应冰川均衡调整;（2）使用冰川均衡调整校正的坡度准确估计洪水流量;（3）将海洋和更广泛的气候系统的响应与新改进的总淡水通量估计相联系。将进行冰川均衡调整模拟，以预测古地形和古斜坡的沼泽地。洪水排泄路径和洪水流量估计将使用冰川均衡调整校正后的地形计算。最后，这些新的淡水通量的估计将比较的地球化学记录的沉积物芯收集的俄勒冈州海岸，以评估海洋的生物系统的响应特大洪水事件。这项拟议的研究超越了多个尺度，使用冰川均衡调整模型将地貌过程与地幔对冰负荷的响应的小波长和大波长特征联系起来，最终连接本地短-该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响进行评估来支持审查标准。

Dr. Tamara Pico has been awarded an NSF EAR Postdoctoral Fellowship to investigate the influence of glacial isostatic adjustment on late Pleistocene catastrophic flooding to improve our understanding of the timing and routing of mega-floods. The work will be conducted at the California Institute of Technology and Oregon State University. During the last ice age, 22,000 to 14,000 years ago, dozens of catastrophic mega-floods from an ice-dammed Glacial Lake Missoula scoured the landscapes of Idaho and eastern Washington, forming what are known as the Channeled Scablands. These glacial lake outbursts are the largest known floods on Earth. Reconstructing the magnitude of these events informs our understanding of how floods shape Earth's landscapes and relate to abrupt changes in climate. Over the period of flooding, ice sheet melting caused crustal deformation with rates of about 10 mm/yr, which is orders of magnitude above regional tectonic uplift rates, resulting in a substantially different regional topography relative to today. This process of glacial isostatic adjustment has been neglected in prior estimates of flood volumes or discharge, introducing a potentially large error, which has not yet been quantified. This study will provide a more accurate estimates of total discharge during flood events which in turn will help quantify the response of the ocean and broader climate system to mega-floods. In addition, the research will help inform for outburst flood planning by studying the nature of past catastrophic flooding and the stability of ice sheets in response to climate change. The PI has extensive leadership and outreach experience in women in science and underrepresented minority groups and will continue a committed involvement in these communities. Outburst mega-floods from glacial Lake Missoula, occurring from 22,000 to 14,000 years ago, are the largest known floods on Earth. Prior estimates of water volume and flow discharge during these flood events rely on slopes based on modern topography. Over this time period, glacial isostatic adjustment caused crustal deformation with rates of about 10 mm/yr, orders of magnitude above regional uplift rates, and changed local slopes by about 30%. Thus, prior estimates of flood volumes include a potentially large error, which has not yet been quantified. Furthermore, over the interval of Missoula flooding, patterns of uplift and subsidence due to glacial isostatic adjustment evolved significantly, and this reshaping of topography may explain observed changes in flood routing over time. This proposal, within disciplines of Geomorphology and Geophysics, seeks to investigate the influence of glacial isostatic adjustment on the Channeled Scablands landscape as it developed over the course of Missoula mega-flood events. Three interconnected goals for this project are proposed: (1) reconstruct drainage path evolution across the interval of flood events in response to glacial isostatic adjustment; (2) accurately estimate flood discharge using slopes corrected for glacial isostatic adjustment; and (3) connect the response of ocean, and broader climate system, to newly-refined estimates of total freshwater flux. Glacial isostatic adjustment simulations will be performed to predict paleo-topography and paleo-slopes in the Channeled Scablands. Flood drainage pathways and flood discharge estimates will be calculated using the resulting topography corrected for glacial-isostatic adjustment. Finally, these new estimates of freshwater flux will be compared to the geochemical record of sediment cores collected off the Oregon coast, to assess the response of the ocean's biological system to mega-flood events. The proposed research, which transcends multiple scales by using glacial-isostatic adjustment modeling to connect geomorphic processes to both small and large wavelength features of the mantle's response to ice loading, ultimately linking local short-lived outburst flooding to longer global climate changes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.