[A-OS11] Ocean Mixing Frontiers

[AOS11-02] Small-scale topographic effects on the generation of along-shelf propagating internal solitary waves on the Amazon Shelf

*Xiaolin Bai¹、Kevin Lamb¹、Jose C. B. da Silva² (1.Department of Applied Mathematics, The University of Waterloo, Canada、2.Department of Geosciences, Environment, and Spatial Planning, and Instituto Ciencias da Terra (ICT), Polo Porto, Porto, Portugal)

キーワード：Internal solitary wave, Along-shelf propagation, Small-scale topography, ISW-induced mixing

In this talk, we consider the joint effects of tidal and steady currents to investigate internal wave generation and propagation on the Amazon shelf, a hotspot for internal solitary wave (ISW) generation. The Amazon Shelf is off the mouth of the Amazon River in the southwest tropical Atlantic Ocean, affected by strong tidal constituents over complex bottom bathymetry and a strong western boundary current, the North Brazilian Current (NBC). Satellite observations and numerical modelling are used in this study. Satellite observations provide a clear visualization of the wave characteristics, such as temporal and spatial distributions, propagating direction and its relation to background currents. These ISWs appear as streak-like patterns in satellite images along a narrow path within the NBC propagating against the current. Near-critical conditions (Froude number close to 1) created by the NBC and tide result in strong ISW generation, while the dominant subcritical conditions result in the upstream propagation of these ISWs. Their streak-like patterns are a result of the quasi-two-dimensional bathymetry below, suggesting the possibility of using sea surface imprints to detect the topographic features beneath. This study demonstrates that small-scale topographic features can result in a rich generation of ISWs, which are expected to significantly contribute to ocean mixing and, potentially, sediment resuspension. The ISW-induced current also contributes to sea surface wave breaking as observed by satellites.