Characterization and mechanism of resuspension events induced by internal tides at the toe of Shenhu canyon

• Six resuspension events were observed through digital video images at the toe of Shenhu Canyon at water depth of 1405 m. • Although smaller particles (0.6–6 mm) were numerically dominant, they do not contribute as significantly to the total particle volume as larger particles (>10 mm). • The intensity of resuspension triggered by down-slope propagating fronts was greater than that by up-slope propagating fronts. • The interaction of internal tides with the sloping topography induced SIE-IGW regime was associated with the resuspension events. Understanding sediment resuspension in deep-sea (primarily deeper than 1000 m) environments is critical for environmental impact assessments and engineering planning. To investigate these processes, a lander was deployed at a depth of 1405 m at the toe of the Shenhu Canyon in the northern South China Sea. Equipped with sensors measuring near-bottom current velocity, temperature, turbidity, and a digital video camera, the lander recorded six resuspension events. Suspended particulate matter (SPM) concentrations were derived from video analysis, revealing that smaller particles (0.6–6 mm) often dominated in number but contributed less to the total volume compared to larger particles (>10 mm). Analysis of current velocity and temperature variations identified distinct resuspension mechanisms. Two events were triggered by down-slope propagating fronts, likely driven by the oblique propagation of internal tides and flow over a nearby promontory. Four events resulted from up-slope propagating fronts caused by internal tide breaking. Down-slope events exhibited greater intensity than up-slope ones. Wavelet analysis of temperature data revealed sub-inertial frequencies during the resuspension events, associated with a dynamical regime known as the sub-inertial event and internal gravity wave (SIE-IGW) regime. The slope of the canyon is near critical and supercritical, which is also consistent with this regime. This study enhances our understanding of resuspension processes in deep-sea environments, highlighting the interplay between internal tides, seafloor topography, and particle distribution, contributing to improved predictions of sediment dynamics.