Characterization and mechanism of burst resuspension events at the toe of Shenhu canyon

Understanding sediment resuspension processes in deep-sea environments is crucial for informing environmental impact assessments and making efficient planning of engineering operations. In this study, we deployed a lander at the toe of the Shenhu Canyon on the northern slope of South China Sea at a water depth of 1450 m to investigate deep-sea sediment resuspension processes. The lander was equipped with different sensors to measure near-bottom current velocity, temperature, turbidity, and digital videos. Several burst resuspension events were recorded. The suspended particular matter (SPM) concentration was calculated by analyzing the digital videos. The deep-sea digital video analysis showed that sometimes smaller particles were numerically dominant, but they do not contribute as significantly to the total particle volume as larger particles. Different resuspension mechanisms are identified by analyzing the characteristics of near-bottom current velocity and temperature variation. Two short-term burst resuspension events were attributed to up-slope propagating fronts arising from the nonlinear effect of internal tides. Another short-term burst resuspension event was triggered by a down-slope propagating front, likely generated by the oblique propagation of internal tides and the flow over a nearby promontory. The intensity of the short-term burst resuspension event triggered by the down-slope propagating front was greater than others triggered by up-slope propagating fronts. Other long-term burst resuspension events were induced by internal tides. The wavelet analysis of temperature data indicated that a distinct sub-inertial frequency during the resuspension period, which was consistent with the presence of a dynamical regime known as the sub-inertial event and internal gravity wave (SIE-IGW) regime, was associated with the burst resuspension events. This research contributes to the knowledge of burst resuspension processes in deep-sea environments, enhancing our understanding of the complex interplay between internal tides, seafloor topography, and the distribution of suspended particles.