Internal Tides, Mixing and the Bottom Boundary
Layer
Internal Tides, Mixing and the Bottom Boundary
Layer
James Girton and Eric KunzeAPL/UW and Univ. Victoria
James Girton and Eric KunzeAPL/UW and Univ. Victoria
Monterey Canyon Internal TidesMonterey Canyon Internal Tides
From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)
Beams and Flux DivergenceBeams and Flux Divergence
From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)
Critical ReflectionCritical Reflection
From Nash, Kunze, Toole, and Schmitt (JPO 2004)From Nash, Kunze, Toole, and Schmitt (JPO 2004)
Internal wave breaking mixes stratified fluid near boundary
Successive mixing events and subsequent collapse lead to gradual dispersal of boundary layer fluid away from margin
Fluorescein-dyed boundary layer fluid spreading into the interior.
Shadowgraph image: subcritical internal wave breaking against a sloping boundary.
Bottom Boundary MixingBottom Boundary Mixing
From McPhee-Shaw and Kunze (JGR 2002)From McPhee-Shaw and Kunze (JGR 2002)
Flux Co-SpectraFlux Co-Spectra
k co-S[u’p’](k)
k co-S[w’p’](k)
kin
krefl
krefl
kin
kin krefl kin krefl
k co-S[u’p’](k)
k co-S[w’p’](k)
kin
krefl
krefl
kin
kin krefl kin krefl
BBL Bores in the CanyonBBL Bores in the Canyon
From Rosenfeld et al (‘Aha 1999)From Rosenfeld et al (‘Aha 1999)
Survey BoxSurvey Box 8 occupations of 9 stations (72 XCPs) over 12.4 hours, followed by microstructure time-series.
5 km 5 km box, resolves M2 and M4 harmonic.
Additional 1/2-hourly XCP+microstructure time-series for 12.4 hours at one spot to resolve high-frequency variability
Max XCP depth = 2000 m; profiles to 1 m above bottom
Processes/ObservablesProcesses/Observables
• Energy flux divergence vs. local dissipation• Near-critical reflection (bispectra)• Bottom boundary-layer stress and bores• Stratification flux from boundary
• Nonlinearity of semidiurnal tide (M4)
• Impact of wave-field coherence on mixing parameterizations
• Energy flux divergence vs. local dissipation• Near-critical reflection (bispectra)• Bottom boundary-layer stress and bores• Stratification flux from boundary
• Nonlinearity of semidiurnal tide (M4)
• Impact of wave-field coherence on mixing parameterizations
TPXO Surface TidesTPXO Surface Tides
From Klymak and Pinkel proposalFrom Klymak and Pinkel proposal
Now Where?Now Where?
• Slope North of Bay• Corrugated Topography• Submarine Fan• Broad Ridge South of Bay
• Slope North of Bay• Corrugated Topography• Submarine Fan• Broad Ridge South of Bay
Additional Proposed Work (NSF)Additional Proposed Work (NSF)
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Timing/Location CriteriaTiming/Location Criteria
• 3 cycles of the semidiurnal tide (close to spring)
• Less than 2000 m water depth• Probably site survey near FLIP• Strong internal tides and 2-D geometry
preferred
• 3 cycles of the semidiurnal tide (close to spring)
• Less than 2000 m water depth• Probably site survey near FLIP• Strong internal tides and 2-D geometry
preferred