EAR-PF: Experimental study of the dynamics of frozen, cohesive river banks: bridging pore-scale properties with channel-scale dynamics.

基兰·邓恩博士被授予NSF EAR博士后奖学金，研究北极大范围融化对冰冻河岸侵蚀变化的影响，以及对温室气体和重金属排放的影响。这项工作将在加州理工学院迈克尔·兰姆博士的指导下进行。北极气候变化的加速正在导致永久冻土(通常全年保持冻结状态的冰和土壤)的大范围融化。多年冻土的流失导致河岸变弱，河道迁移，加快了温室气体和重金属的释放。这些环境问题加上河流形状的变化，导致北极地区的社区流离失所。该项目旨在描述永久冻土河岸的组成对北极河岸侵蚀和河道迁移速度的影响。这项工作包括一系列实验，以确定控制侵蚀和河流迁移的特性，有助于建立一个框架，改进极地地区的河流系统管理，并更好地了解全球碳循环。该项目还包括教育和外联活动，纳入了加州理工学院为高中生和本科生提供的现有项目。邓恩博士还计划在SedEdu上开发和分发有关河流过程的在线教育模块。SedEdu.北极的大片土地上，河流横贯其中，由永久冻土组成。多年冻土基质中孔隙冰的存在已被证明对侵蚀岸坡材料有深远的影响，因为孔隙冰大大提高了冻土相对于未冻土的屈服强度。因此，永冻土的侵蚀速率对气候驱动的当地水文和大气温度条件的变化高度敏感。这项研究试图从机理上理解冻土成分和水温对冻结河岸侵蚀速率的影响。将进行一系列实验，以确定粘性沉积物对控制北极地区河岸侵蚀速度的永久冻土基质的热机械和岩土性质的影响。这一实验方法将与对北极天然永久冻土河流的高分辨率卫星图像的分析相结合，以确定河岸侵蚀和横向迁移率在一年中如何随着实验室探索的管理机制的变化而变化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Kieran Dunne has been awarded an NSF EAR Postdoctoral Fellowship to study the effects of widespread thawing in the Arctic on changes in frozen riverbank erosion and on the release of greenhouse gasses and heavy metals. The work will take place under the mentorship of Dr. Michael Lamb at California Institute of Technology. Accelerating climate change in the Arctic is leading to the widespread thawing of permafrost (ice and soil that typically remains frozen throughout the year). The loss of permafrost results in weakening of riverbanks, river channel migration and speeds up the release of greenhouse gasses and heavy metals. These environmental issues combined with changes in the shape of rivers have led to the displacement of communities in the Arctic. This project seeks to characterize the ways that the composition of permafrost riverbank impacts the rate of riverbank erosion and river channel migration in the Arctic. The work includes a series of experiments to determine the properties that control erosion and river migration, contributing to a framework for improved management of river systems in polar regions and a better understanding of the global carbon cycle. The project also includes education and outreach activities that incorporate preexisting California Institute of Technology programs for high school and undergraduate students. Dr. Dunne also plans to develop and distribute online educational modules on river processes hosted on SedEdu.Huge regions of land in the Arctic through which rivers incise are comprised of permafrost. The presence of pore ice in permafrost substrates has been shown to have a profound effect on the erodibility bank material as pore ice greatly increases the yield strength of frozen soil relative to unfrozen soil. As a result, the erosion rates of permafrost soils are highly sensitive to climate-driven changes to both local hydrological and atmospheric temperature conditions. This study seeks to develop a mechanistic understanding of the effects of permafrost composition and water temperature on the erosion rate of frozen riverbanks. A suite of experiments will be performed to determine the effects of cohesive sediment on the thermomechanical and geotechnical properties of permafrost substrates that govern the rate of riverbank erosion in Arctic regions. This experimental approach will be coupled with analysis of high-resolution satellite imagery of natural, permafrost rivers in the Arctic to determine how rates of channel bank erosion and lateral migration changes throughout the year in response to the governing mechanisms explored in the lab.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.