Effects of Sea Level Rise on Tidal Dynamics in Macrotidal Hangzhou Bay

Abstract

Sea level rise (SLR) due to climate change is expected to alter tidal processes and energy transport, disproportionately affecting coastal communities. Utilizing a nested hydrodynamics model, we provided an integrated investigation of tidal responses to SLR in the Hangzhou Bay (HZB). The scenarios of SLR in the next hundred years count for both non-uniform trends based on historical altimetry data and uniform trends from the latest IPCC projections. In a comparison of model results under different SLR scenarios, we found that the tidal range is amplified by SLR in HZB with stronger amplification at the shallow southern coast. Tidal range change generally increases with the SLR scale; however, neglecting the heterogeneities in the spatial distribution of SLR tends to overestimate the SLR effects. The harmonic analysis illustrates that SLR exaggerates the dominated semidiurnal tides (M2 and S2) but dampens their overtides and compound tides (M4, M6, and MS4), of which M2 amplitude amplification explains 71.2–90.0% of tidal range change. SLR tends to promote tidal energy entering HZB through the Zhoushan Archipelago (ZA) compared to the prototype, while dampened sea-bed roughness and reduced tidal velocity come with a less dissipative environment in HZB, resulting in 6–18% more tidal energy exported upstream. Numerical experiments indicate ZA has significant effects on tidal responses and energy flux generation, therefore, its quantitative influences and physical mechanism are also discussed in this paper.

Impact of sea level rise on tidal energy budget in a macro-tidal coastal bay with archipelago

“…Previous studies on tidal energy dissipation in Hangzhou Bay have primarily focused on bottom friction (Wu et al, 2018;Liang et al, 2022). Liang et al (2022) found that bottom dissipation increases around the Zhoushan Archipelago and the Andong tidal flat, while decreasing in other areas of Hangzhou Bay with SLR, consistent with this study.…”

“…The contribution of the Greenland and Antarctic ice sheets, glaciers, and groundwater storage is from Fox-Kemper et al (2021). Liang et al (2022) estimated the rate of glacial isostatic adjustment (GIA) in Hangzhou Bay is 0.12 mm yr -1 . Wang et al (2012) estimated that the rate of land subsidence in the northern Hangzhou Bay can be up to 2 mm yr -1 .…”

“…The coastlines of the islands in Zhoushan Archipelago are intricate, with narrow waterways and rugged seabed topography, resulting in high shear, strong current, and nonlinear tide (Hou et al, 2015). Liang et al (2022) found that Zhoushan Archipelago leads to an uneven increase in tidal amplitude along the two shores and promotes the formation of local progressive waves. However, it is still unclear how the strong horizontal shear in the archipelago region contributes to tidal energy dissipation and how the dissipation responds to SLR, thus affecting the tidal amplitudes in the upper reach of the bay.…”

Impact of Tides and Surges on Fluvial Floods in Coastal Regions

“…This surge model considers the interaction between tides and surges while neglecting the effect of waves whose contribution to surges is less than 5% [25]. This surge model has been validated for historical typhoon events, showing good agreement with previous observations [36].…”

“…The model resolution varies from 37 km offshore to 60 m nearshore, and results were stored at a 1 h temporal resolution. Details about the nested model schematization and parameterization are introduced in the article of Liang et al [36]. The nested model uses astronomic tidal levels derived from the NAOTIDE global model (NAO.99b), as well as mean sea level pressures of 10 m meridional (v; northward) and zonal (u; westward) wind components from the ERA5 reanalysis dataset, with a spatial resolution of 15 arcmins and a temporal resolution of 1 h. To ensure coherence between the flood drivers, the atmospheric forcing of the river routing model and surge model was based on the same ERA5 reanalysis dataset, with a significantly enhanced one-hour temporal resolution [35].…”