The critical role of stratification in submarine channels: Implications for channelization and long runout of flows
The critical role of stratification in submarine channels: Implications for channelization and long runout of flows
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DOI：
10.1002/2014jc009807
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发表时间：
2014-04-01
影响因子：
3.6
通讯作者：
Wynn, R. B.
中科院分区：
文献类型：
--
作者：
Dorrell, R. M.;Darby, S. E.;Wynn, R. B.
沟道化的海底重力流可以传播很远的距离，将沉积物输送到海底扇的远端。然而，在这些距离上维持流动的机制仍然是个谜。在本文中，我们考虑了两个浅水模型，第一个模型假设水流是非分层的，而第二个模型用经验模型来描述垂直分层，它影响深度平均质量和动量传递。通过与模拟流动动力学的比较，阐明了分层的重要性。结果表明，垂直分层模式对黑海信道化的场尺度重力流的现场观测数据具有最好的拟合效果。此外，与非分层模型中的水流相比，分层水流受渠道的限制程度要大得多。然而，这两个模型都不能准确地表示系统远端的流动动力学，这表明现有的经验分层模型需要改进才能准确地描述场尺度的重力流。它还强调了弱分层小规模实验在描述现场尺度过程方面的局限性。结果表明，在现实世界系统中，分层很可能使航道内的流速和流量保持不变，从而促进沉积物在低海底坡度上悬浮数百公里。这解释了水流如何能够传播很远的距离，并将其沉积物输送到海底扇的远端。关键点密度驱动流的垂直分层增加了径流长度现有经验模型预测流动分层分层可以解释海底扇末端沙叶的形成
Channelized submarine gravity currents travel remarkable distances, transporting sediment to the distal reaches of submarine fans. However, the mechanisms by which flows can be sustained over these distances remain enigmatic. In this paper we consider two shallow water models the first assumes the flow is unstratified whilst the second uses empirical models to describe vertical stratification, which effects depth averaged mass and momentum transfer. The importance of stratification is elucidated through comparison of modeled flow dynamics. It is found that the vertically stratified model shows the best fit to field data from a channelized field-scale gravity current in the Black Sea. Moreover, the stratified flow is confined by the channel to a much greater degree than the flow in the unstratified model. However, both models fail to accurately represent flow dynamics in the distal end of the system, suggesting current empirical stratification models require improvement to accurately describe field-scale gravity currents. It also highlights the limitations of weakly stratified small-scale experiments in describing field-scale processes. The results suggest that in real-world systems stratification is likely to enable maintenance of velocity and discharge within the channel, thus facilitating sediment suspension over distances of hundreds of kilometers on low seafloor gradients. This explains how flows can travel remarkable distances and transport their sediment to the distal parts of submarine fans.Key Points Vertical stratification of density-driven flows enhances runout length Existing empirical models under predict flow stratification Stratification may explain formation of sandy lobes at the end of submarine fans