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East-west asymmetry in nonlinear internal waves from Luzon Strait

East-west asymmetry in nonlinear internal waves from Luzon Strait
East-west asymmetry in nonlinear internal waves from Luzon Strait
The nonhydrostatic Regional Ocean Modeling System is applied to study the effects of thermocline shoaling/deepening, bathymetry, and asymmetric modulated tides on the soliton growth to the west and east of Luzon Strait in the South China Sea and western Pacific Ocean. Luzon Strait comprises a shallow east ridge and a deep west ridge, and its interaction with barotropic tidal currents yields strong westward internal tides that disperse into solitons. Satellite imagery indicates that the westward solitons are more numerous and better defined than the eastward solitons. The model results show that the eastward solitons are 45%, 39%, 28%, and 23% smaller than the westward solitons due to asymmetric modulated barotropic tides at the east ridge, a deeper Pacific Ocean, westward thermocline shoaling related to the Kuroshio current, and internal tide resonance in a double ridge configuration, respectively. Due to the westward location of the Kuroshio, little thermocline deepening occurs east of the east ridge. Hence, the influence of thermocline deepening on counteracting eastward soliton growth is small. The Kuroshio mainly enhances westward soliton growth. The dispersion of internal tides into solitons is governed by the balance between the nonlinearity parameter on the one hand and the nonhydrostatic and Coriolis dispersions on the other. It is shown that this balance favors soliton growth for thermocline shoaling, while it counters it for a deeper ocean. A series of double ridge experiments is performed, in which the distance between the ridges and the height of the west ridge are varied. For a semidiurnal tidal forcing and two Gaussian ridges separated by 100 km, barotropic to baroclinic energy conversion is enhanced at both ridges, causing larger westward internal tides and solitons. The combination of Coriolis forcing, thermocline shoaling, and a double ridge configuration enhances the distinctiveness of the so-called type a and b solitons when a modulated tide occurs.

0148-0227
C10057
Buijsman, M.C.
34e571e8-f11f-47f5-9297-cde570e7af90
McWilliams, J.C.
845b39d5-d3f8-44fc-9332-3235c8d405c3
Jackson, C.R.
ada916e0-0c34-4b90-9bc1-cb4e29ebf831
Buijsman, M.C.
34e571e8-f11f-47f5-9297-cde570e7af90
McWilliams, J.C.
845b39d5-d3f8-44fc-9332-3235c8d405c3
Jackson, C.R.
ada916e0-0c34-4b90-9bc1-cb4e29ebf831

Buijsman, M.C., McWilliams, J.C. and Jackson, C.R. (2010) East-west asymmetry in nonlinear internal waves from Luzon Strait. Journal of Geophysical Research, 115 (C10), C10057. (doi:10.1029/2009JC006004).

Record type: Article

Abstract

The nonhydrostatic Regional Ocean Modeling System is applied to study the effects of thermocline shoaling/deepening, bathymetry, and asymmetric modulated tides on the soliton growth to the west and east of Luzon Strait in the South China Sea and western Pacific Ocean. Luzon Strait comprises a shallow east ridge and a deep west ridge, and its interaction with barotropic tidal currents yields strong westward internal tides that disperse into solitons. Satellite imagery indicates that the westward solitons are more numerous and better defined than the eastward solitons. The model results show that the eastward solitons are 45%, 39%, 28%, and 23% smaller than the westward solitons due to asymmetric modulated barotropic tides at the east ridge, a deeper Pacific Ocean, westward thermocline shoaling related to the Kuroshio current, and internal tide resonance in a double ridge configuration, respectively. Due to the westward location of the Kuroshio, little thermocline deepening occurs east of the east ridge. Hence, the influence of thermocline deepening on counteracting eastward soliton growth is small. The Kuroshio mainly enhances westward soliton growth. The dispersion of internal tides into solitons is governed by the balance between the nonlinearity parameter on the one hand and the nonhydrostatic and Coriolis dispersions on the other. It is shown that this balance favors soliton growth for thermocline shoaling, while it counters it for a deeper ocean. A series of double ridge experiments is performed, in which the distance between the ridges and the height of the west ridge are varied. For a semidiurnal tidal forcing and two Gaussian ridges separated by 100 km, barotropic to baroclinic energy conversion is enhanced at both ridges, causing larger westward internal tides and solitons. The combination of Coriolis forcing, thermocline shoaling, and a double ridge configuration enhances the distinctiveness of the so-called type a and b solitons when a modulated tide occurs.

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Published date: 29 October 2010
Organisations: Ocean and Earth Science

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Local EPrints ID: 340318
URI: http://eprints.soton.ac.uk/id/eprint/340318
ISSN: 0148-0227
PURE UUID: 02f6e516-7faf-4433-830b-da8f6166eff4

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Date deposited: 18 Jun 2012 14:38
Last modified: 04 Nov 2019 20:40

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