Abstract:

Internal tides (ITs) are internal waves (IWs) with tidal frequency. ITs are ubiquitous in a stratified ocean where they are generated in response to tidal flows incident upon bottom topography. Studies on ITs have attracted considerable attention over the years, because these waves can have a significant impact on oceanic mixing, large scale ocean circulation, transport of energy, upwelling of nutrients and shaping the continental shelves. Along-shelf currents or boundary currents are ocean currents commonly observed along coastlines. We investigated the effects of a geostrophic current on the propagation and generation of ITs by performing numerical experiments using the MITgcm.

As for the propagation of the ITs through a background current, most of the theoretical work is based on linear theories. A number of numerical studies dedicated to linear IW-mesoscale interactions used ray tracing techniques and linear modal decomposition. The research we have done contributed to the understanding of the interaction between a nonlinear current and ITs, where the ITs are generated outside of the current and later propagate into the current.

As for the generation of the ITs, most research is relatively basic in the sense that only the effect of barotropic tides and bathymetry is considered in the IW generation process. We have built on past work by investigating IT generation over a shelf in the presence of an along-shelf geostrophic current, which is a common feature along continental shelf. Our focus was on the barotropic to baroclinic energy conversion rate and the IT beam pattern.

Biography:

Dr. Yangxin He is a physical oceanographer who has a passion to understand the physical dynamics of internal waves. She received her MSc and PhD degrees from the University of Waterloo, Canada under the supervision of Dr. Kevin Lamb. Her PhD thesis focuses on the theoretical and numerical studies of the internal solitary waves with a trapped core, propagation and generation of linear internal waves under the influence of a geostrophic background current. Dr. Yangxin He's interests include nonlinear waves, linear internal waves and computational fluid mechanics.