Topographic height dependence of internal wave generation by tidal flow over random topography

Author :Jiajun Zhao, Likun Zhang, Harry L. Swinney
Publication :Geophysical Research Letters
Publisher :Geophys. Res. Lett.
Volume :42
Number :8081'8087
Year :2015
DOI: : 10.1002/2015GL065650

Internal waves (IWs) generated by tidal flow over the seafloor play a critical role in ocean circulation and climate. We determine the dependence of the radiated IW power on topographic parameters in numerical simulations of tidal flow over two-dimensional random topographic profiles that have the spectrum of oceanic abyssal hills. The IW power increases as the horizontal spatial resolution scale is decreased, but below a certain spatial scale the power saturates at a level less than the linear theory prediction. For increasing topographic height $H_\mathrm{rms}$ the emergent interference between waves radiated by neighboring peaks leads to a transition in the IW power dependence on $H_\mathrm{rms}$ from quadratic to linear. This transition in the scaling of the IW power depends on the slopes of a valley’s nearest neighboring peaks.  Our results should guide the modeling of IW generation by tidal flow over small-scale ocean topography.