EAR-PF: The impact of varying sediment supply on Arctic delta-front transport processes

美国国家科学基金会博士后奖学金已被授予博士Brandee N。卡尔森在博尔德市科罗拉多大学的Irina Overeem博士的指导下开展研究和教育活动。该项目旨在评估融化的冰盖和冰川以及融化的永久冻土如何增加沉积物供应，从而影响北极三角洲的增长。输送到北极三角洲，特别是西格陵兰的沙子，被认为是全世界海岸恢复工作和工业用途（主要是混凝土生产）的潜在资源。该项目将利用实地观测和遥感技术调查控制沿着北极海岸线沉积物滞留的过程。这项工作将为格陵兰沙的使用政策和经济决定提供信息。此外，从这个项目中获得的信息将用于开发一个面向入门本科生的学习模块，允许用户探索对增量增长的控制。该模型将存放在SedEdu，这是一套与地貌学和沉积学有关的教育工具，水下三角洲前缘沉积物输运过程是沿海演变的重要控制因素。河流和水下异重流是地球表面沉积物再分布的最大机制。水下海岸的演变很容易通过历史和卫星图像观察到，但量化水下沉积物运动本质上是困难的，因为它通常需要在现场观察。三角洲前缘沉积物输运过程对于快速增长的高沉积速率三角洲尤为重要。在气候变暖的条件下，北极三角洲，特别是格陵兰的三角洲，正在迅速增长，因为它们从融化和退缩的冰川和融化的永久冻土中获得了更多的沉积物供应。虽然有证据表明，三角洲前缘的故障，运输大量的沉积物，目前还不清楚在何种程度上，他们影响三角洲的侵蚀率和沉积物滞留沿着海岸线。这项研究将容易观察到的数据（陆上三角洲活动的图像）与水下沉积物输运过程联系起来。本研究的目的是确定陆上三角洲活动如何与水下三角洲前缘的沉积物输送联系起来，以及沉积物供应的增加如何影响北极三角洲的海洋沉积物输送过程。反过来，三角洲前故障三角洲顶集动态的影响将进行评估。这些问题将在不同的时间和空间尺度上加以讨论。Carlson博士将利用重复测深数据，在可变流量条件下，在一个现场位置评估单个三角洲前缘迁移事件。在这一实地活动期间，将利用卫星图像评估陆上三角洲顶面（例如湿润区）的变化。三角洲顶集活动和三角洲前缘输运时间/位置之间的相关性将用于推断过去条件下的关系（使用34年的陆地卫星数据进行评估），并考虑未来条件下的三角洲前缘沉积物输运（例如，北极三角洲前缘故障如何在变暖气候下更高的水和沉积物排放条件下变化？）。这些研究结果可能会提供深入了解的条件和潜在影响，转移沉积物输送在格陵兰岛的其他峡湾三角洲。地球科学部的地貌学和土地利用动力学项目共同资助了该奖学金。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An NSF EAR Postdoctoral Fellowship has been awarded to Dr. Brandee N. Carlson to carry out research and education activities under the mentorship of Dr. Irina Overeem at the University of Colorado, Boulder. The project seeks to assess how enhanced sediment supply from melting ice sheets and glaciers, and thawing permafrost impacts the growth of Arctic deltas. The sand delivered to Arctic deltas, particularly those in West Greenland, is recognized as a potential resource for coastal restoration efforts and for industrial use (primarily concrete production) worldwide. This project will investigate the processes that control sediment retention along Arctic coastlines using field observations and remote sensing. This work will inform policy and economic decisions for sand-use in Greenland. Furthermore, the information gained from this project will be used to develop a learning module geared toward introductory undergraduate students that allows the user to explore controls on delta growth. The model will be housed at SedEdu, which is a suite of educational tools related to geomorphology and sedimentology.Subaqueous delta-front sediment transport processes are an important control on coastal evolution. Rivers and subaqueous density flows are the largest mechanisms for sediment redistribution on Earth's surface. Subaerial coastal evolution is easily-observable through historical and satellite imagery, however quantifying subaqueous sediment movement is inherently difficult because it typically requires observation in the field. Delta-front sediment transport processes become especially important to consider for rapidly growing deltas with high sedimentation rates. Under warming climate conditions, Arctic deltas, particularly those in Greenland, are rapidly growing as they receive enhanced sediment supply from melting and retreating glaciers and thawing permafrost. While there is evidence for delta-front failures that transport substantial volumes of sediment, it is unclear to what degree they influence delta progradation rates and sediment retention along coastlines. This study links readily observable data (images of subaerial delta activity) to subaqueous sediment transport processes. The objectives of this study are to determine how subaerial delta activity links to sediment transport at the subaqueous delta front and how enhanced sediment supply impacts marine sediment transport processes on Arctic deltas. In turn, the influence of delta-front failures on delta topset dynamics will be evaluated. These questions will be addressed over different temporal and spatial scales. Dr. Carlson will evaluate individual delta-front transport events at one field location during variable discharge conditions, using repeat bathymetric data. During this field campaign, changes in the subaerial delta topset (e.g. wetted area) will be evaluated using satellite imagery. Correlations between delta topset activity and delta-front transport timing/location will be used to infer relationships under past conditions (evaluated using 34 years of Landsat data) and to consider delta-front sediment transport under future conditions (e.g. how do Arctic delta-front failures vary under higher water and sediment discharge conditions in a waring climate?). These findings may offer insight into the conditions and potential effects of shifting sediment delivery for other fjord deltas in Greenland. The Geomorphology and Land-use Dynamics program in the Earth science division is co-funding this fellowship.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.