HR: 0800h
AN: OS21B-1230    [Abstracts]
TI: Evolution of Internal Waves in Monterey Bay
AU: * Jachec, S M
EM: sjachec@stanford.edu
AF: Dept. of Civil & Environmental Engineering, Environmental Fluid Mechanics Laboratory, Stanford University, Stanford, CA 94305 United States
AU: Fringer, O B
EM: fringer@stanford.edu
AF: Dept. of Civil & Environmental Engineering, Environmental Fluid Mechanics Laboratory, Stanford University, Stanford, CA 94305 United States
AU: Gerritsen, M
EM: margot.gerritsen@stanford.edu
AF: Dept. of Petroleum Engineering, Stanford University, Stanford, CA 94305 United States
AU: Street, R L
EM: street@stanford.edu
AF: Dept. of Civil & Environmental Engineering, Environmental Fluid Mechanics Laboratory, Stanford University, Stanford, CA 94305 United States
AB: Recently, it has been hypothesized (e.g., Munk and Wunsch, and Briscoe and Muller) that internal waves propagating near coastal boundaries may play an important role in the global budgets of mixing and dissipation. Lien and Gregg, and Gregg and colleagues cite that highly-concentrated intermittent patches of turbulence and enhanced dissipation exist over ridges and within canyons; this is consistent with internal wave findings by Petruncio and with ideas from Garrett and Munk who suggest that instability and internal wave breaking are likely mechanisms for mixing through turbulence. According to Hickey as much as 50% of the world's coastal ocean may be composed of canyons, ridges, and gullies. Therefore, exists a need to understand the interaction between complex bathymetry and internal waves. One such location is Monterey Bay, CA, a location known to possess a well-defined submarine canyon, internal waves, and elevated dissipation. Although field experiments, such as the Internal Tide EXperiments (ITEX), and prior numerical simulations of Monterey Bay by Petruncio, Rosenfeld, and Paduan from the Naval Postgraduate School, and scientists from other universities have expanded the knowledge of the interaction between internal waves and bathymetry, the evolution of the internal wave field under realistic physical conditions and over complex bathymetry is not fully understood. Some shortcomings of their simulations were summarized by Rosenfeld and others; improvements suggested include nonhydrostatic simulations, and finer grid resolution. These suggestions seem reasonable because high frequency processes are present; these processes include canyon bores, solitons, and possibly breaking internal waves. The purpose of this work is to describe the evolution of an internal wave field under realistic physical conditions and over a representative portion of the Monterey Bay's complex bathymetry. This is accomplished by use of the Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator (SUNTANS) to obtain the velocity field. We describe the generation and propagation portion of the internal wave life-cycle. Subsequently, these internal wave AŸA›A›ƒ_sAªA.ƒ_odataAŸA›A›ƒ_sAª are processed using Hilbert-Huang Transforms (HHTs). HHTs provide a new and unique way of presenting spectra in contrast to traditional Fourier and wavelet methods. The HHT yields time-frequency-energy spectra, which may be used to describe the time-dependency of internal wave energy along with frequency as these waves propagate toward the coastline. By extracting numerical AŸA›A›ƒ_sAªA.ƒ_odataAŸA›A›ƒ_sAª from strategic locations along the cross-section, not only can the time-evolution of the wave be tracked, but also the cross-shore evolution can be portrayed. By using a combination of numerical simulations and signal processing, the evolution of the internal wave field is characterized under realistic field conditions.
UR: http://suntans.stanford.edu
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
DE: 4544 Internal and inertial waves
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting