Can extreme internal waves trigger turbidity currents and carbon transport in submarine canyons?

科学背景：海底峡谷通过沿大陆坡向下输送富含沉积物的浑浊流和冷咸密度流，在将沉积物和碳从陆架海输送到深海中发挥关键作用。这些洋流是零星的，触发它们的过程人们知之甚少，因此它们对全球沉积物和碳收支的总体贡献仍然不确定。一种建议的触发机制涉及由海洋潮汐产生并聚焦到海底峡谷的大幅度内(次表层)波。内波增加了近床面的水流速度，特别是高能的内波事件可能会使足够多的泥沙重新悬浮，形成浑浊流。项目目标：1)调查内波如何使沉积物和碳重新悬浮。2)确定触发阈值。3)确定峡谷下方的沉积物和碳的传输。研究方法：您将分析惠塔德峡谷的长期水动力、沉积学和生物地球化学数据，惠塔德峡谷是一个切割凯尔特海大陆架的大型分支海底峡谷系统。使用自主海洋滑翔机和声学多普勒海流剖面仪(ADCP)系泊数据，您将首先绘制峡谷内波的空间和季节变化图，以确定最有可能触发事件的地点和时间。然后，使用来自沉积物圈闭和生物地球化学传感器的数据，您将研究内波使沉积物和碳重新悬浮的机制，确定触发阈值，并量化峡谷下方的沉积物和碳运输。最后，你将把惠塔德峡谷的结果与世界各地的其他峡谷系统进行比较。

Scientific background:Submarine canyons play a key role in the transport of sediment and carbon from shelf seas to the deep ocean by funnelling sediment-laden turbidity currents and cold-salty density currents down the continental slope. These currents are sporadic and the processes that trigger them poorly understood, so their overall contribution to global sediment and carbon budgets remains uncertain. One proposed triggering mechanism involves large-amplitude internal (subsurface) waves, which are generated by ocean tides and focused into submarine canyons. Internal waves increase near-bed current speed and particularly energetic internal wave events may resuspend enough sediment to form turbidity currents. Project objectives:1) Investigate how internal waves resuspend sediment and carbon.2) Identify triggering thresholds.3) Determine down-canyon sediment and carbon transport.Research methodology:You will analyse long-duration hydrodynamic, sedimentological and biogeochemical data from Whittard Canyon, a large branching submarine canyon system that incises the Celtic Sea continental shelf. Using autonomous ocean glider and acoustic Doppler current profiler (ADCP) mooring data, you will first map the spatial and seasonal variability of internal waves within the canyon to identify where and when triggering events are most likely. Then, using data from sediment traps and biogeochemical sensors, you will investigate the mechanisms by which internal waves resuspend sediment and carbon, identify triggering thresholds, and quantify down-canyon sediment and carbon transport. Finally, you will compare your results from Whittard Canyon with other canyon systems worldwide.