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

科学背景：海底峡谷在陆架海向深海输送沉积物和碳的过程中起着关键作用，它将含沙的浊度流和冷盐密度流汇集到大陆斜坡上。这些洋流是零星的，人们对触发它们的过程知之甚少，因此它们对全球沉积物和碳收支的总体贡献仍然不确定。一种被提出的触发机制涉及由海潮产生并集中到海底峡谷的振幅较大的内部（地下）波。内波增加了近床水流的速度，特别是高能内波事件可能使足够的沉积物重新悬浮起来，形成浊流。项目目标：1)研究内波对沉积物和碳的再悬浮作用。2)确定触发阈值。3)确定峡谷下游沉积物和碳输运。研究方法：您将分析来自惠塔德峡谷的长期水动力学，沉积学和生物地球化学数据，这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电流分析器（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，利用沉积物陷阱和生物地球化学传感器的数据，您将研究内波重新悬浮沉积物和碳的机制，确定触发阈值，并量化峡谷下的沉积物和碳运输。最后，你将把你从惠塔德峡谷得到的结果与世界上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.