Abstract. Mean sea-level (MSL) is rising worldwide, and correlated changes in ocean tides are also occurring; their combination may influence future total sea-levels (TSL), possibly increasing coastal inundation and nuisance flooding events in sensitive regions. Analyses of a set of tide gauges in Hong Kong and in the South China Sea (SCS) reveal complex tidal behavior. Most prominent in the results are strong correlations of MSL variability to tidal variability which may further increase local flood levels under future MSL rise. We also highlight inter-tidal correlations of diurnal (D1) tides to semidiurnal (D2) tides, positively reinforced through the northern SCS, and the correlations of overtide (OT) fluctuations to D1 and D2, negatively reinforced (i.e., anti-correlated) across the same region, thought to be related to the baroclinic energetics in the Luzon Strait and the Taiwan Strait. The baroclinic signals may be enhanced at the northern shelf of the SCS and can generate PSI interactions that may amplify minor tides such as M3. Additionally, there are anomalous tidal events observed in some enclosed harbor regions of Hong Kong, corresponding to times of rapidly changing MSL as well as rapid coastal development projects. Results support the hypothesis that the observed variability is due to multiple spatial processes, best described as an amplification of the local (Hong Kong) tidal response to the prevailing regional (SCS) tidal patterns, enhanced by local harbor changes. A close analysis of the full-spectrum tidal response suggests that a change in the resonant and frictional response may have occurred.
Tidal variability in the ionospheric dynamo region
