Propagation of internal tides generated near Luzon Strait: Observations from autonomous gliders

Rainville, Luc; Lee, Craig M.; Rudnick, Daniel L.; Yang, Kai-Chieh

doi:10.1002/jgrc.20293

Cited by 45 publications

(43 citation statements)

References 43 publications

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“…This study and others conducted in the Pacific (e.g., Rudnick et al 2011;Davis et al 2012;Rainville et al 2013) demonstrate how observations from autonomous underwater gliders can provide long-duration, high-resolution observations within strong boundary currents. Here we have shown how these glider observations can be used to produce estimates of the potential vorticity, a key dynamical property of the North Atlantic western boundary current.…”

Section: Discussionsupporting

confidence: 63%

Potential Vorticity Structure in the North Atlantic Western Boundary Current from Underwater Glider Observations

Todd

Owens

Rudnick

2016

Journal of Physical Oceanography

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Potential vorticity structure in two segments of the North Atlantic's western boundary current is examined using concurrent, high-resolution measurements of hydrography and velocity from gliders. Spray gliders occupied 40 transects across the Loop Current in the Gulf of Mexico and 11 transects across the Gulf Stream downstream of Cape Hatteras. Cross-stream distributions of the Ertel potential vorticity and its components are calculated for each transect under the assumptions that all flow is in the direction of measured vertically averaged currents and that the flow is geostrophic. Mean cross-stream distributions of hydrographic properties, potential vorticity, and alongstream velocity are calculated for both the Loop Current and the detached Gulf Stream in both depth and density coordinates. Differences between these mean transects highlight the downstream changes in western boundary current structure. As the current increases its transport downstream, upper-layer potential vorticity is generally reduced because of the combined effects of increased anticyclonic relative vorticity, reduced stratification, and increased cross-stream density gradients. The only exception is within the 20-km-wide cyclonic flank of the Gulf Stream, where intense cyclonic relative vorticity results in more positive potential vorticity than in the Loop Current. Cross-stream gradients of mean potential vorticity satisfy necessary conditions for both barotropic and baroclinic instability within the western boundary current. Instances of very low or negative potential vorticity, which predispose the flow to various overturning instabilities, are observed in individual transects across both the Loop Current and the Gulf Stream.

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Section: Discussionsupporting

confidence: 63%

Potential Vorticity Structure in the North Atlantic Western Boundary Current from Underwater Glider Observations

Todd

Owens

Rudnick

2016

Journal of Physical Oceanography

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“…Field measurements near one deep channel on the eastern ridge observed isopycnal displacements of 200-300 m high [Pinkel et al, 2012]. Recent field measurements using gliders, moored, and shipboard instruments revealed the internal tide radiation from the Luzon Strait [Johnston et al, 2013;Rainville et al, 2013;Rudnick et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

Internal tide radiation from the Luzon Strait

2014

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The M 2 , K 1 , and O 1 internal tides originating in the Luzon Strait are investigated using the sea surface height measurements by multiple satellites ERS-2, Envisat, TOPEX/Poseidon, Jason-1/2, and Geosat Follow-On. A plane wave fit method is used to resolve multiple internal tides in arbitrary horizontal directions. The Luzon Strait is an energetic internal tide generation site, and radiates internal tides both westward into the South China Sea (SCS) and eastward into the western Pacific (WP). In the SCS, the K 1 and O 1 internal tides propagate over 1600 km, reaching the Vietnam coast; in the WP, they propagate over 2500 km and arrive to the Mariana Ridge and Guam. The K 1 and O 1 internal tides refract toward the Equator during propagation. The M 2 internal tides in the SCS bifurcate into two beams. The northwestward beam is coincident with the frequent occurrence of internal solitary waves in this region, implying their causative relation. The phase speeds inferred from the altimetric along-beam propagation agree with the theoretical values. Due to the influence of the Earth's rotation, the K 1 and O 1 phase speeds decrease remarkably from high to low latitudes. For the diurnal internal tides, the eastward radiation is about 50% greater than the westward radiation. For M 2 , the westward radiation is about two times the eastward radiation. The altimetric energy fluxes are about 50% of those in numerical model simulations.

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“…the largest internal tides in the ocean, with depth-integrated energy fluxes >60 kW m −1 , are generated at two parallel ridges in Luzon Strait (Alford et al, 2011;. Averaging over many glider missions, considerable asymmetry is found between eastward and westward propagation into the Pacific Ocean or South China Sea (Rainville et al, 2013;). Here we focus on the waves, which propagate westward into the South China Sea, steepen, and produce large-amplitude internal waves on the shallow thermocline.…”

Section: Report Documentation Pagementioning

confidence: 99%