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Abstract The M2internal tides in the northeastern South China Sea are studied using satellite altimeter data from 1992–2018. By an improved mapping technique that combines plane wave analysis and two‐dimensional spatial filtering, multiple internal tides are separately extracted with weak internal tides becoming detectable. The satellite results reveal for the first time a 300‐km‐long southward M2internal tidal beam in the northeastern South China Sea. The generation source is on the steep continental slope at the southern entrance to the Taiwan Strait. It ranges from 118–120°E along 22°N. Combining satellite‐observed internal solitary waves and internal tides, it is found that the onshore radiation evolves into nonlinear solitary waves and the offshore radiation in the form of linear internal tides. Based on the 26‐year‐coherent satellite results, the integrated southward energy flux is 0.18 GW, about 10% of the westward energy flux from the Luzon Strait. In the northeastern South China Sea, the westward and southward internal tides form a multiwave interference field, which features significant spatial variations in the magnitude and direction of energy flux. Further analyses reveal that the steep continental slope radiates southward semidiurnal M2and S2internal tides, but not diurnal K1and O1internal tides.
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Seasonal West‐East Seesaw of M2 Internal Tides From the Luzon Strait
Satellite altimetry sea surface height (SSH) measurements from 1993 to 2017 are used to investigate the seasonal variability of mode‐1 M2internal tides from the Luzon Strait. The 25 years of SSH data are divided into four seasonal subsets, from which four seasonal internal tide models are constructed following the same mapping procedure. Climatological seasonal hydrography in the World Ocean Atlas 2013 is used to calculate two seasonally variable parameters required in the mapping procedure: Wavelength and the transfer function from the SSH amplitude to depth‐integrated energy flux. The M2internal tides from the Luzon Strait are extracted using propagation direction determined in plane wave analysis. The satellite results show that the westward and eastward M2internal tides both demonstrate significant seasonal variation. The westward and eastward internal tides seesaw seasonally: The westward internal tides strengthen (weaken) in summer and fall (winter and spring); while the eastward internal tides strengthen (weaken) in winter and spring (summer and fall). We suggest that the seasonal seesaw is mainly determined by ocean stratification and the Kuroshio Current; however, further studies are needed to quantify their relative contributions.
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- PAR ID:
- 10635943
- Publisher / Repository:
- Wiley Publisher
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 128
- Issue:
- 3
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1029/2022JC019281
