The description of hydrodynamics associated with the extensive reef system on the shelf break adjacent to the Amazon River is still a challenge for ocean sciences. Despite the discharge of more than one billion tons of cohesive sediment per year, the outer continental shelf of the world's largest river presents very low concentrations of suspended sediment near the bottom and an absence of modern fine sediment deposits nearly one hundred kilometers before the shelf break. The offshore limit of the subaqueous delta consists of a sigmoidal clinoform standing between 40 and 70 m in depth, a depositional feature that cannot be explained solely by estuarine-like gravitational circulation. This paper aims to test the hypothesis that internal tides have a major role in the control of offshore fine sediment transport. For that, we implement a set of tridimensional, non-hydrostatic, and high-resolution (up to 2 m, vertical, and 2 km, horizontal) Delft3D models. The experiments showed that even disregarding river plume buoyancy, wind drag, superficial waves, and ocean currents, the exclusive interaction between barotropic tidal currents, bathymetry, and the stratification structure of the ocean is capable of generating asymmetrical current patterns compatible with modern deposition. The maximum shelf slope and the relative depth between the outer shelf and the pycnocline represent the main factors influencing the generation and shoreward propagation of internal tides. Over time, spring-neap cycles are eventually capable of reverting cross-shore subtidal transport tendencies, while seasonal variability in ocean stratification modulates the intensity of baroclinic processes.

对与亚马逊河相邻的陆架断裂上的广泛礁石系统相关的水动力的描述仍然是海洋科学的挑战。尽管每年排放超过十亿吨的粘性沉积物，但世界上最大的河流的外大陆架在其底部附近的悬浮沉积物浓度非常低，并且在支架破裂前将近一百公里处没有现代精细沉积物。水下三角洲的离岸界限包括一个呈乙状的斜面形，深达40至70 m，这是一种沉积特征，不能仅仅通过类似河口的重力循环来解释。本文旨在检验以下假设：内部潮汐在控制海上精细沉积物运输中起主要作用。为了那个原因，我们实现了一组三维，非静液压和高分辨率（水平方向最大2 m，水平方向最大2 km）的Delft3D模型。实验表明，即使不考虑河羽浮力，风阻，表面波浪和洋流，正压潮汐流，测深法和海洋分层结构之间的排他性相互作用也能够产生与现代沉积相适应的不对称洋流模式。最大的架子坡度和外部架子与比索克林之间的相对深度代表了影响内部潮汐产生和向海岸传播的主要因素。随着时间的流逝，春季小潮周期最终能够逆转潮间带的潮汐运输趋势，而海洋分层的季节性变化会调节斜压过程的强度。