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Physics of estuaries and coastal seas
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Seasonal Alternation of Tidal Asymmetry Induced by Mean Sea Level Variation
Monday 7th @ 1110-1130, Conference Hall
Yunwei Wang* , Hohai University
Qian Yu, Nanjing University
Shu Gao, East China Normal University
Presenter Email: ms.ywwang@gmail.com |
| Asymmetries are important characteristics of the coastal tide, which determine the direction and magnitude of tide-induced sediment transport. In a tidal channel of the south Yellow Sea coast, China, hourly sea-level data were observed continuously from January 2013 to December 2016 by a tidal gauge. Throughout the 4 years, seasonal changes of tidal asymmetry were indicated by harmonic analysis, which is flood-dominant in winter while ebb-dominant in summer. The seasonal alternation of tidal asymmetry can be interpreted by the seasonal variation of mean sea level (MSL). In winter, monthly MSL is below the annual mean value, leading to a smaller tidal range and ratio of intertidal storage (Vf) to channel volume (Vc), and thereby to flood-dominant tide. Instead, in summer, the higher MSL results in a larger tidal range and Vf/ Vc as well, and thus the tide is ebb-dominant. The pattern of flood and ebb dominant tide alternation indicates the equilibrium of tidal basin morphology by balancing the onshore and offshore sediment transport in winter and summer, respectively. It is analogized that the sea level rise (SLR) in the future will result in ebb-dominant tide, and the offshore net sediment transport will consequently further enhance coastal erosion. This study provides a typical example of the coastal response to SLR for similar environments. |
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