Publication Date:
2016-02-27
Description:
This study presents two sets of current records obtained from the South China Sea and satellite altimeter data, and it suggests that near-inertial waves induced by parametric subharmonic instability (PSI) associated with internal tides can be transported poleward beyond their critical latitude φ c by background geostrophic flow (BGF). The two mooring locations were poleward of φ c (≈14°N) for diurnal subharmonics (0.5 D 1 ; half diurnal frequency D 1 ); however, both of the current records revealed clear signals at 0.5 D 1 . The enhanced sub-inertial motion at 0.5 D 1 exhibited a fortnightly spring-neap cycle but did not agree with that of D 1 , indicating that it may not be generated via PSI associated with the local D 1 . Observations from the altimeter data and a ray-tracing simulation suggested that these non-locally generated 0.5 D 1 waves may be excited near their φ c , after which they propagated poleward under the role of the BGF to the observation site with a latitude higher than φ c . The poleward propagation of near-inertial waves can produce elevated vertical shears; thus, it may play an important role in enhancing the local turbulent mixing. This article is protected by copyright. All rights reserved.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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