Multidomain observations of internal wave-induced shelf-to-basin sediment transport in the Eastern Levant Basin

Shelf-to-basin sediment transport plays a key role in the evolution of continental margins and the carbon cycle. Yet, the mechanisms linking oceanographic forcing to sediment resuspension and redistribution remain poorly quantified. Intermediate nepheloid layers (INLs) are widely recognized as substantial sediment conveyors in this context, but their formation mechanisms, morphologic imprint, and spatio-temporal evolution remain elusive in direct observations and process-based interpretation.
Here, we present multidomain observations from the Eastern Levant Basin (ELB) that document the internal-wave-induced origin and seasonal recurrence of INLs. We integrate ultra-high-resolution (decimeter-scale) multichannel Seismic Oceanography (SO), high-resolution bathymetry, in situ conductivity-temperature-depth (CTD) profiles, oceanographic reanalysis products from the Copernicus Marine Service, and spaceborne Synthetic Aperture Radar (SAR) imagery, to link water-column stratification, internal wave activity, sediment resuspension, sediment transport, and their morphologic outcomes. These data sets span multiple years and capture the same processes during comparable seasonal stratification regimes, allowing assessment of process persistence rather than isolated events.  

Our results show that during periods of strong seasonal column stratification (i.e., Brunt-Vaisälä frequencies in the order of N ≈ 0.01 s⁻¹), shoaling internal waves promote sediment resuspension from the shelf edge and basinward transport. Seismic profiles reveal laterally continuous, gently inclined low-amplitude reflection packages with thicknesses of up to 10 meters that detach from the seabed and are interpreted as INLs flowing up to 10 km from the continental slope. This is confirmed by in-situ CTD measurements showing aligned water-column turbidity peaks up to 10 kilometers offshore the area of resuspension. Calculated internal wave (IW) beam angles relative to local slope show a clear correlation between transmissive (subcritical) zones, seafloor erosion, and locations of sediment detachment, while reflective (supercritical) areas show the appearance of sediment-wave patterns interpreted as upslope-migrating steps. Our results are consistent across different years and geophysical datasets. Co-located SAR imagery independently confirms the presence and orientation of internal wave packets during these periods.

Together, these observations provide robust field-based evidence that internal wave-driven sediment mobilization is a seasonally recurrent process, governed by water-column stratification and seafloor criticality.  These observations link sediment transport, oceanographic dynamics, and slope geomorphology in an increasingly stratified, warming ocean.