Sediment Resuspension and Transport by Internal Solitary Waves

Abstract

Large-amplitude internal waves induce currents and turbulence in the bottom boundary layer (BBL) and are thus a key driver of sediment movement on the continental margins. Observations of internal wave–induced sediment resuspension and transport cover significant portions of the world's oceans. Research on BBL instabilities, induced by internal waves, has identified several mechanisms by which the BBL is energized and sediment may be resuspended. Due to the complexity of the induced currents, process-oriented research using theory, direct numerical simulations, and laboratory experiments has played a vital role. However, experiments and simulations have inherent limitations as analogs for oceanic conditions due to disparities in Reynolds number and grid resolution, respectively. Parameterizations are needed for modeling resuspension from observed data and in larger-scale models, with the efficacy of parameterizations based on the quadratic stress largely determining the accuracy of present field-scale efforts.

Shoaling mode-2 internal solitary-like waves

“…In figure 10 (a), it can be seen that the down-slope flow (black) rides up and over the separation bubble (bottom white) near x = 5.52 m. The separation region subsequently grows in vertical extent, leading to vortex roll up and the generation of short length scale variations. The bottom boundary layer dynamics are similar to those observed under mode-1 ISWs of depression and are attributed to an adverse pressure gradient at the trailing edge of the wave and "global instability" in the boundary layer (Bogucki et al 1997;Hammond & Redekopp 1998;Stastna & Lamb 2002;Diamessis & Redekopp 2006;Carr et al 2008;Boegman & Ivey 2009;Boegman & Stastna 2019). The numerical results corroborate the experimental observation that the shoaling mode-2 wave can induce boundary layer separation before the terminal phase of shoaling.…”

“…Sutherland et al (2013) demonstrate that shoaling-induced breaking regimes of mode-1 ISWs can be classified successfully in terms of the bed slope s and an internal Iribarren † number Ir = s/(s w ) 1/2 , subject to careful definition of the length scale L w . A thorough review of these studies and related field observations can be found in Boegman & Stastna (2019). In this paper, a similar range of s and Ir to those in the studies above are considered.…”

“…Internal solitary waves (ISWs) continue to attract burgeoning interest, not least because of their pervasiveness in many marine and freshwater environments (Horn et al 2001;Nash & Moum 2005;Helfrich & Melville 2006;Groeskamp et al 2011;Lamb 2014;Bourgault et al 2016;Boegman & Stastna 2019). They propagate on density interfaces in stably-stratified fluid systems and may be characterised generally as nonlinear, dispersive waves of quasi-permanent form with an amplitude comparable with the thickness of the interface on which they travel and also, in many cases of interest, the overall depth of the fluid system in question (see e.g.…”

Commentary: Variability in Shelf Sedimentation in Response to Fluvial Sediment Supply and Coastal Erosion Over the Past 1,000 Years in Monterey Bay, CA, United States

“…• Sediment transport from internal waves-including landward transport of slope and outer shelf sands and seaward transport of inner shelf sands-as documented in Monterey Bay and similar settings (Cacchione et al, 2002;Noble and Xu, 2003;Storlazzi et al, 2003;Cheriton et al, 2014;Rosenberger et al, 2016;Boegman and Stastna, 2019).…”

Bumpy Topographic Effects on the Transbasin Evolution of Large‐Amplitude Internal Solitary Wave in the Northern South China Sea

“…Because of the strong bottom currents induced by shoaling ISWs, many sand dunes composed of fine to medium sand are reported to be formed on the upper continental slope region in the northern SCS (Ma et al, ; Reeder et al, ). The further response of shoaling ISWs to this kind of topographic bumps, which are at least 1 order of magnitude smaller than the prominent bumps studied here, is unclear as yet due to the limit of model resolution and the complexity of associated sediment resuspension and transport processes (Boegman & Stastna, ; Stastna & Lamb, ). Besides, due to the influence of background current, distinct processes of convective breaking and trapped core phenomena of shoaling ISWs (Lamb, , ) are observed near the Dongsha region between the realistic sections R1 and R2 (Lien et al, ; Lien et al, ).…”