Ocean process-driven sediment transport in submarine canyons along the northern Cascadia margin: Morphological control of triggers

卡斯卡迪亚北部边缘海底峡谷中海洋过程驱动的沉积物输送：触发因素的形态控制

• 批准号: 2147983
• 负责人: Andrea Ogston
• 金额: $ 82.98万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147983&HistoricalAwards=false
• 关键词: Ocean; process; driven; sediment; transport

“Ocean process-driven sediment transport in submarine canyons along the northern Cascadia margin: Morphological control of triggers”Submarine canyons act as a major highway between the coastal and deep ocean, transporting enough water, nutrients, and sediment to have a global impact on geology, biology, and climate. Just like canyons on land, submarine canyons are large, eroded valleys, but they are not carved by rivers. Instead, submarine canyons are carved by downslope-flowing currents of sediment and water akin to an avalanche. Scientists are challenged in predicting the onset and distance traveled by these flows. This project aims to identify the physical processes in these flows off the coast of Washington and learn how differences in canyon structure can affect the flows generally. A set of seafloor instruments in two submarine canyons will be installed to record sediment gravity flows as they pass through them. These data are quite rare and greatly aid understanding of flow mechanics and enable development of numerical models that predict where and when flows occur. Six seafloor instrument packages will be maintained in Astoria Canyon and Quinault Canyon, both fed by the Columbia River, for a complete year. Sediment cores will be collected from both canyons, where event-layers from past sediment-gravity flows will be identified and analyzed for their composition and historical frequency. The researchers predict that river floods and marine storm events (large waves, strong winds) can trigger major sediment gravity flows in these canyons today, but differences in canyon terrain trigger sediment-gravity flows under different conditions. Submarine canyons are present along nearly every continental margin and are the sites of globally significant ocean mixing, sediment transport, and nutrient exchange between the coastal and abyssal environment. Earth’s submarine canyons are maintained by density-driven flows of water and sediment, but the mechanisms that trigger flows—and their downslope flow evolution—are still not well understood. This project examines the pathways of sediment through two canyons along Cascadia Margin which are morphologically distinct yet share the same fluvial source, the Columbia River. This study’s experimental design includes a targeted instrument deployment, comprehensive seabed coring survey, and hydrodynamic modeling of sediment gravity flows. The project is intended to advance knowledge of canyon sedimentary processes under modern high stands in sea level and constrain the role of morphology and oceanographic disturbance in initiating seabed resuspension and density-driven flow. Seafloor sediment loading from fluvial sources, triggering of flows by bathymetric focusing of wave and current energy, and synchronous downslope transport across distant canyon systems will be studied as functions of canyon morphology in Astoria and Quinault Canyons. The investigators predict that sedimentary deposits in relatively deep-water canyon environments may be created via oceanic triggering, and aim to place quantitative constraints on the downslope limit of such flows. They also predict that processes in differing canyon morphologies result in deposits that are both regionally synchronously and asynchronously emplaced at depth.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.

“卡斯卡迪亚北部边缘海底峡谷中海洋过程驱动的沉积物输送：触发因素的形态控制”海底峡谷是沿海和深海之间的主要高速公路，输送足够的水、营养物和沉积物，对地质产生全球影响就像陆地上的峡谷一样，海底峡谷是巨大的、被侵蚀的山谷，但它们不是由河流雕刻而成的，而是由下坡水流雕刻而成的。科学家们面临着预测这些水流的爆发和行进距离的挑战，该项目旨在确定华盛顿海岸附近这些水流的物理过程，并了解峡谷结构的差异如何影响水流。将在两个海底峡谷中安装一套海底仪器来记录沉积物流经峡谷时的重力流，这些数据非常罕见，有助于理解流动力学，并能够开发预测流动地点和时间的数值模型。六海底发生。仪器包将在阿斯托利亚峡谷和奎诺特峡谷进行维护，这两个峡谷均由哥伦比亚河供水，将从这两个峡谷收集沉积物岩心，在那里将识别和分析过去沉积物重力流的事件层。研究人员预测，河流洪水和海洋风暴事件（大浪、强风）可以在今天的这些峡谷中引发主要的沉积物重力流，但峡谷地形的差异会在不同的条件下引发沉积物重力流。峡谷几乎存在于每个大陆边缘，是全球重要的海洋混合、沉积物运输以及沿海和深海环境之间养分交换的场所，地球的海底峡谷是由密度驱动的水和沉积物流动维持的，但其机制却是这样的。该项目研究了沿着卡斯卡迪亚边缘的两个峡谷的沉积物路径，这两个峡谷在形态上不同，但共享相同的河流源头哥伦比亚河。本研究的实验设计包括有针对性的仪器部署、全面的海底取芯调查和沉积物重力流的水动力模型，该项目旨在增进对现代高海平面下峡谷沉积过程的了解，并限制形态和海洋扰动的作用。 . 在启动海底再悬浮和密度驱动的流动中，来自河流源的海底沉积物加载、通过波浪和海流能量的测深聚焦触发流动以及跨越遥远峡谷系统的同步下坡输送将被研究。研究人员预测，相对深水峡谷环境中的沉积物可能是通过海洋触发形成的，并旨在对此类流动的下坡限制进行定量限制。他们还预测了不同的过程。峡谷形态导致沉积物在深度区域同步和异步沉积。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准。