Scattering of coastal-trapped waves by irregularities in coastline and topography
type: CreativeWork
description: A study is conducted of the scattering of freely-propagating subinertial frequency coastal-trapped waves (CTWS) by large variations in coastline and topography using analytical and numerical techniques. Particular attention is paid to the role of stratification because, as shown, the introduction of even modest stratification can eliminate backscattered free-waves with large wavenumbers which occur, theoretically, in a barotropic ocean. An analytical solution is presented for the scattering of barotropic waves incident upon a discontinuity in shelf width. Discussion of solutions relying on backscattered free-waves is avoided by considering only the range of parameters over which energy transmission is nearly 100%. The solution shows there is a substantial transfer of energy to modes other than that of the incident wave. The transmitted mode most readily excited is that which has the across-shelf structure most closely coinciding with that of the incident wave. For a widening shelf, energy is therefore readily transferred to higher modes. The resultant presence of multiple modes produces a strong modulation in flow intensity and phase progression downstream of the scattering region which may affect the interpretation of shelf wave observations. A non-dispersive shelf wave 'pulse' of limited a10ngshelf extent scatters into a train of similarly shaped waves of all allowable modes, each propagating at its own free-wave speed. To overcome limitations of the analytical study a numerical model which accomodates arbitrary density stratification, bathymetry, and coastline, is employed. Numerical simulations are conducted of the scattering of CTWs by a set of topographic and coastline variations which are representative of many continental shelves. The strength of the scattering observed is found to be proportional to a topographic warp factor which estimates the severity of the topographic irregularities. The scattering is amplified by density stratification. A comparison of…
abstract: A study is conducted of the scattering of freely-propagating subinertial frequency coastal-trapped waves (CTWS) by large variations in coastline and topography using analytical and numerical techniques. Particular attention is paid to the role of stratification because, as shown, the introduction of even modest stratification can eliminate backscattered free-waves with large wavenumbers which occur, theoretically, in a barotropic ocean. An analytical solution is presented for the scattering of barotropic waves incident upon a discontinuity in shelf width. Discussion of solutions relying on backscattered free-waves is avoided by considering only the range of parameters over which energy transmission is nearly 100%. The solution shows there is a substantial transfer of energy to modes other than that of the incident wave. The transmitted mode most readily excited is that which has the across-shelf structure most closely coinciding with that of the incident wave. For a widening shelf, energy is therefore readily transferred to higher modes. The resultant presence of multiple modes produces a strong modulation in flow intensity and phase progression downstream of the scattering region which may affect the interpretation of shelf wave observations. A non-dispersive shelf wave 'pulse' of limited a10ngshelf extent scatters into a train of similarly shaped waves of all allowable modes, each propagating at its own free-wave speed. To overcome limitations of the analytical study a numerical model which accomodates arbitrary density stratification, bathymetry, and coastline, is employed. Numerical simulations are conducted of the scattering of CTWs by a set of topographic and coastline variations which are representative of many continental shelves. The strength of the scattering observed is found to be proportional to a topographic warp factor which estimates the severity of the topographic irregularities. The scattering is amplified by density stratification. A comparison of…
author: Wilkin, John L.
language: en_US
keywords: Ocean waves
date published: 1988-09
date modified: 2026-07-27T22:05:06Z
provider: Woods Hole Oceanographic Institute
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Massachusetts Institute of Technology and Woods Hole Oceanographic Institution

PropertyValue
property ID: Handle
value: https://hdl.handle.net/1912/4956

PropertyValue
property ID: DOI
value: 10.1575/1912/4956