Observation of internal tidal currents in the Kaoping Canyon off southwestern Taiwan

Wang, Y.H.; Lee, I.H.; Liu, James T.

doi:10.1016/j.ecss.2008.07.016

Cited by 30 publications

(33 citation statements)

References 20 publications

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“…The observation that the K 1 tide dominates the Gully is highly unusual. Previous studies of canyons at similar latitudes have unanimously shown the highest tidal velocities occur at the M 2 frequency [ Hotchkiss and Wunsch , 1982; Petruncio et al , 1998; Kunze et al , 2002; Wang et al , 2008; Lee et al , 2009]. The explanation of enhanced M 2 tidal velocities has concentrated on geometric focusing of the free M 2 internal tide by supercritical canyon topography [ Hotchkiss and Wunsch , 1982] and local in‐canyon generation on critical bottom slopes [ Petruncio et al , 2002].…”

Section: Discussionmentioning

confidence: 99%

“…The available observations [ Hotchkiss and Wunsch , 1982; Huthnance , 1989; Petruncio et al , 1998; Kunze et al , 2002; Wang et al , 2008; Lee et al , 2009] show an increase in tidal energy toward the bottom, and head of the respective canyons. The observed amplification usually exceeded that expected from linear geometrical funneling, invoking the internal tide focusing mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Resonant amplification of subinertial tides in a submarine canyon

Swart¹,

Allen²,

Greenan³

2011

J. Geophys. Res.

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[1] Tidal oscillations dominate the flow field in many submarine canyons. Observations have shown that semidiurnal tidal energy in submarine canyons is significantly amplified with respect to adjacent shelves. This amplification is thought to be caused by focusing of propagating internal tides incident from the open ocean, or local in-canyon generation on critical canyon floor slopes. These mechanisms require freely propagating internal tides, with superinertial frequencies. We present results from a moored array in a canyon at 44°N, where the observed velocities reached over 0.8 m s −1 . The canyon flow field was highly unusual because it was dominated by the subinertial diurnal tide. This occurred despite the fact that the barotropic tide was predominantly semidiurnal. The diurnal tide was dramatically amplified in the canyon, its velocities increasing toward the seafloor and canyon head. The diurnal oscillations also exhibited marked modulation in time by the background barotropic forcing. Length scales suggest that the diurnal tide should be resonant in the canyon. An analytical framework is used to explain the mechanisms behind the strong diurnal currents observed by the moored array. In the model, along-shelf barotropic flow sets up a double Kelvin wave response in the canyon, generating along-canyon velocities which are subsequently amplified by resonance. The pattern of the model predictions is in excellent agreement with the observed velocity pattern.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resonant amplification of subinertial tides in a submarine canyon

Swart¹,

Allen²,

Greenan³

2011

J. Geophys. Res.

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“…[] indicate that the internal tide energy flux during this period was predominantly mode‐one. Work in Kaoping Canyon, which is also sinuous, also found that the first mode dominated but also observed large mode‐two amplitudes near the head of the canyon as the slope became supercritical [ Wang et al ., ].…”

Section: Tidal Propagation Through the Upper Canyon During The First mentioning

confidence: 99%

Propagation and dissipation of the internal tide in upper Monterey Canyon

Wain

Gregg

Alford

et al. 2013

J. Geophys. Res. Oceans

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[1] Submarine canyons are sites of intense turbulence and mixing. Monterey Canyon cuts into the continental shelf off California, and is defined by its sinuous nature. Temperature, salinity, and current velocity measurements were made over 21 days in April 2009 with a depth-cycling towed body to understand internal tide propagation and dissipation through the canyon bends. Cross-canyon transects reveal complex flow patterns that follow largescale bathymetry on scales greater than 5 km. Changes in thalweg direction deflect baroclinic energy flux, but the bends in the measurement region are too sharp for the flux to follow the thalweg. Ridges that form the bends in the canyon act as obstacles to the flow, and turbulent dissipation rates greater than 1 Â 10 À5 m 2 s À3 were observed on their flanks, especially at the largest meander (the Gooseneck). The canyon-integrated baroclinic energy flux increased from 2.7 MW at the most western section to 3.7 MW at the Gooseneck Ridge, which has a nearly critical bottom slope with respect to the semidiurnal baroclinic tide on the western side; baroclinic energy flux was 50% less on the eastern side of the ridge. While measured dissipation near the Gooseneck Meander was sufficient to explain the flux divergence, turbulence near the Gooseneck may have been undersampled. Between the Gooseneck Ridge and the most eastern cross-canyon transect, dissipation may account for the decrease in the energy flux; though a local energy balance does not hold, the energy budget is balanced over the larger scale of the measurement region east of the Gooseneck Ridge.

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“…Submarine canyons are also thought to trap internal waves and internal tides originating outside the canyon, through reflection from the sloping topography, and channel the energy towards the canyon floor (Gordon and Marshall, 1976) and canyon head (Hotchkiss and Wunsch, 1982). Elevated internal wave energy near the canyon floor and head has been observed in several submarine canyons worldwide (e.g., Wunsch and Webb, 1979;Hotchkiss and Wunsch, 1982;Wang et al, 2008;Lee et al, 2009) and the mechanism is thought to be responsible for high turbulent mixing rates measured near the head of MSC (Lueck and Osborn, 1985;Carter and Gregg, 2002).…”

Section: Introductionmentioning

confidence: 99%

Transition from partly standing to progressive internal tides in Monterey Submarine Canyon

Hall

Alford

Carter

et al. 2014

Deep Sea Research Part II: Topical Studies in Oceanography

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Monterey Submarine Canyon is a large, sinuous canyon off the coast of California, the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward-looking moored ADCPs. The mooring observations measured a near-surface stratification change in the upper canyon, likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling. This change in near-surface stratification caused a transition in the behaviour of the internal tide in the upper canyon from a partly standing wave during pre-upwelling conditions to a progressive wave during upwelling conditions. Using a numerical model, we present evidence that either a partly standing or a progressive internal tide can be simulated in the canyon, simply by changing the initial stratification conditions in accordance with the observations. The mechanism driving the transition is a dependence of down-canyon (supercritical) internal tide reflection from the canyon floor and walls on the depth of maximum stratification. During pre-upwelling conditions, the main pycnocline extends down to 200 m (below the canyon rim) resulting in increased supercritical reflection of the up-canyon propagating internal tide back down the canyon. The large up-canyon and smaller down-canyon progressive waves are the two components of the partly standing wave. During upwelling conditions, the pycnocline shallows to the upper 50 m of the watercolumn (above the canyon rim) resulting in decreased supercritical reflection and allowing the up-canyon progressive wave to dominate.

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Observation of internal tidal currents in the Kaoping Canyon off southwestern Taiwan

Cited by 30 publications

References 20 publications

Resonant amplification of subinertial tides in a submarine canyon

Resonant amplification of subinertial tides in a submarine canyon

Propagation and dissipation of the internal tide in upper Monterey Canyon

Transition from partly standing to progressive internal tides in Monterey Submarine Canyon

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