Internal solitary waves reshaping the seafloor
Abstract
In the Strait of Messina (Italy) tidal currents interacting with underwater ridges generate large amplitude internal solitary waves (SWs) which propagate northward. Previous studies suggest that the sand wave field present in that location could be produced by the action of the bottom boundary current induced by ISWs transition.
In this work, we investigate the role of solitary waves in sediment resuspension and bedforms generation, by linking experimental studies with physical models and real-field observations. Our experiments show that the repeated stroke action induced at the bottom by successive solitary waves can modify an initially flat bottom, leading to the formation of asymmetric bedforms. We investigate the action of 15 different SWs, each characterized by defined geometric and kinematic features. For each case, we generate 400 successive SWs. A digital pressure gauge and a high-resolution acoustic velocimeter allowed us to measure, locally, both pressure and 3D water velocity induced 5 mm from the bottom by each wave. The horizontal pressure gradient and the velocity field induced by those waves cause the boundary layer separation and the consequent reverse flow. Depending on the wave features and on the water depth, the boundary shear stress induced by the reverse flow can exceed the critical value inducing the back motion of the sand particles. We observed, indeed, the generation of a sand-wave field only for 7 cases, for which we obtain an inverse relation between the bed load transport and the mean acceleration induced at the bottom by the SW passage. We also collected hydrographic data during two oceanographic cruises (RITMARE 2016 and MSFD 2017) in the Gioia Basin, where the ISWs interact with a relevant topographic structure of the seabed (the Gioia Canyon). We show evidence of sediment resuspension and mixing associated with ISWs packets transition and we start to explore the role of SWs in reshaping the seafloor.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMOS33C1814L
- Keywords:
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- 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4219 Continental shelf and slope processes;
- OCEANOGRAPHY: GENERAL;
- 4558 Sediment transport;
- OCEANOGRAPHY: PHYSICAL