Collaborative Research: Tidal internal waves that propagate along the coast: Determining how they are generated and how far they travel

Oregon State University, Corvallis OR

Investigators

Abstract

Tidal internal waves arise from the interaction of the surface tide with topography, with their generation, propagation and dissipation forming a key pathway for tidal energy in the ocean. Internal tides can constitute a dominant energy source on continental shelves, where they can lead to processes such as soliton generation, turbulent mixing and cross shelf exchange, with wide ranging implications for transport, biological productivity and near-shore pollution. This study will explore how internal tides are transformed near the shelf break to propagate along the coast and how quickly they decay by radiating some of their energy offshore. In the deep ocean internal tides usually manifest as low vertical mode waves, however, close to the continental shelf break they may take the form of "leaky" (superinertial) baroclinic coastal trapped waves and edge waves. These modal structures are superinertial analogues to the well studied subinertial coastal trapped waves, having a component that radiates along the shelf break. However, they are distinguished from subinertial waves by exhibiting coincident radiation offshore (i.e. "leaking"). The goal of this study is to better understand the nature of internal tides close to the coastal margin, where the presence of leaky baroclinic trapped internal tides may contribute to the along shore variability and propagation of tidal energy. The study will consider the forcing of these waves by both the local astronomical tide, and by remotely incident deep ocean internal tides. The approach will include idealized, linear, two-dimensional (cross-shore) analyses; idealized, three-dimensional, nonlinear numerical simulations of the coastal response to local and remote forcing; and a suite of realistic numerical simulations to investigate leaky trapped internal tide energy along the U. S. West coast due to local and remote forcing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.