We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Southward Internal Tides in the Northeastern South China Sea.
- Authors
Zhao, Zhongxiang
- Abstract
The M2 internal 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 M2 internal 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 M2 and S2 internal tides, but not diurnal K1 and O1 internal tides. Plain Language Summary: Internal tides are internal waves of tidal frequency occur in the interior of the stratified ocean. They mainly originate from topographic scattering of the barotropic tidal motion. Our knowledge of internal tides is mainly limited by the lack of field measurements with sufficient temporal and vertical resolution. Satellite altimetry offers a unique technique that observes internal tides from the space via their centimeter‐scale sea surface fluctuations. Mapping techniques have been developed to extract internal tides from satellite altimeter data. This paper applies a newly developed mapping technique to the northeastern South China Sea and obtains an internal tide field with unprecedented details. Multidirectional internal tides from different generation sites are separately resolved. The satellite observations shed new light on barotropic‐to‐baroclinic conversion, internal solitary waves, multiwave interference, and internal tide energetics in the South China Sea. This paper confirms the uniqueness of satellite altimetry and the usefulness of the new mapping technique in advancing our knowledge of internal tides. This mapping technique can be applied to observe multiple internal tides in other marginal seas. Key Points: The continental slope at the entrance to the Taiwan Strait radiates southward M2 and S2 internal tides, but not O1 and K1 internal tidesThe 26‐year‐coherent southward M2 energy flux is 0.18 GW, about 10% of the westward energy flux from the Luzon StraitThe complicated multiwave internal tide field leads to significant spatial variability of internal tidal energy flux
- Subjects
SOUTH China Sea; OCEAN waves; TIDES; TIDAL flats; MASS budget (Geophysics)
- Publication
Journal of Geophysical Research. Oceans, 2020, Vol 125, Issue 11, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2020JC016554