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Article
Multimodal Internal Waves Generated over a Subcritical Ridge: Impact of the Upper-Ocean Stratification
Journal of Physical Oceanography
  • Xie Jieshuo, Chinese Academy of Sciences
  • Jiayi Pan, Chinese University of Hong Kong
  • David A. Jay, Portland State University
Document Type
Article
Publication Date
3-1-2015
Subjects
  • Internal waves,
  • Tides -- Remote sensing
Abstract

Interaction of barotropic tides with subsurface topography is vital to ocean mixing. Yet the behavior of large-amplitude, nonlinear, internal solitary waves (ISWs) that can cause strong mixing remains poorly understood, especially that of higher-mode and multimodal internal waves. Therefore, a 2.5-dimensional, nonhydrostatic model with adjustable vertical resolution was developed to investigate effects of upper-ocean stratification on tidally induced multimodal internal waves and to show how they are generated by the subcritical ridge where only upward-propagating internal wave beams (IWBs) are present. The effects of the stratification on properties and characteristics of the excited IWBs and on the energy partition of the radiated mode-1 and mode-2 internal waves were investigated based on the model results. Higher modes of internal waves can also be effectively generated in the IWBs by the subcritical topography, and the contribution to IWBs from higher modes increases with the upper-ocean stratification. Mode-2 ISWs can be excited from the IWBs if both the tidal Froude number and the contribution to IWBs from mode-2 waves are sufficiently high ( U0 is the tidal current speed, and c2 is the phase speed of mode-2 waves). In a moderately stratified upper ocean, both mode-1 and mode-2 ISWs can be produced, but for weak (strong) stratification, only mode-1 (mode-2) ISWs are generated. Further, it is found that the distance between two successive mode-1 or mode-2 ISW trains increases linearly with the upper-ocean stratification. The ratio of the kinetic energy to the available potential energy for the mode-2 ISWs increases with the upper-ocean stratification in a strongly stratified ocean.

Description

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The article is available online at: http://dx.doi.org/10.1175/JPO-D-14-0132.1

DOI
10.1175/JPO-D-14-0132.1
Persistent Identifier
http://archives.pdx.edu/ds/psu/16567
Citation Information
Jieshuo Xie, Jiayi Pan, and David A. Jay, 2015: Multimodal Internal Waves Generated over a Subcritical Ridge: Impact of the Upper-Ocean Stratification. J. Phys. Oceanogr., 45, 904–926.