Understanding the Formation of Underwater Waves
Internal solitary waves (ISWs) form under the surface of the ocean. They develop as a propagating pattern along the interface between a near-surface, light water layer and a deeper, heavier layer. Operating like internal tsunamis, large ISWs can control the temperature distribution across the water column, impact the balance of marine ecosystems, and pose great danger to marine engineering and commercial endeavors. How ISWs form and break is therefore of great interest. Peter J. Diamessis, Civil and Environmental Engineering, is working to understand the breaking of ISWs shoaling over gently sloping underwater terrain, due to convective instability.
Convectively breaking ISWs happen when the rear of the wave catches up with the trough, producing a vertical plunging motion. These have been observed over the continental slope in the South China Sea. Diamessis is using analysis of this extensive data set by collaborators at the University of Washington to guide the configuration of massively parallel, high-accuracy, high-resolution simulations of shoaling ISWs.
Previous analysis of this data set has revealed convectively unstable, large-amplitude ISWs with recirculating turbulent cores, but the mechanisms remain unknown. Using two- and three-dimensional simulations, Diamessis’ group is investigating these mechanisms and locations of ISW breaking, taking into account the bottom slope, initial wave steepness, and background baroclinic tidal current.
The improved understanding and quantification of the convective breaking process in shoaling ISWs—in terms of preferred locations of occurrence, underlying physics, turbulent fluxes, and onshore particulate transport—will facilitate the reliable parameterization or incorporation of such processes into larger-scale models, which now effectively cannot resolve the ISWs and associated breaking.