Residual flow and tidal asymmetry in the Singapore Strait, with implications for resuspension and residual transport of sediment

Abstract

.[1] The Singapore Strait connects the South China Sea, where tides are dominantly diurnal, to the dominantly semidiurnal Indian Ocean. At this transition, the tidal water level oscillations are observed to be semidiurnal while the tidal current oscillations are mixed, diurnal to fully diurnal. Due to the interaction of the diurnal constituents with the semidiurnal M 2 tide, the tides are strongly asymmetric. Both residual flows and subtidal flows, with periodicities of 2 weeks to 1 year, are strong. In order to analyze and explain the hydrodynamics around Singapore, a well-documented and calibrated regional tidal model application was further improved and validated. Analysis of the results of this model shows that the diurnal tidal wave is primarily standing, with an amphidromic point close to Singapore, explaining the dominantly diurnal current and semidiurnal water level oscillations. Analysis of the model results further indicates that the fortnightly constituents in the subtidal flow are probably compound tides, with a combined amplitude over 10 cm/s. Pronounced yearly and half-yearly cycles in spring tidal current amplitude and asymmetry exist, resulting from interaction of the diurnal and the semidiurnal spring-neap cycles, compound tides, and the monsoon currents. A simple analytical transport formula was applied to determine the relative importance of tidal asymmetry and residual flows, verified with a full sediment transport model. With fine sediment being more sensitive for residual flow and coarser sediment for tidal flow, a pronounced divergence in sediment transport pathways may exist, depending on the grain size.Citation: van Maren, D. S., and H. Gerritsen (2012), Residual flow and tidal asymmetry in the Singapore Strait, with implications for resuspension and residual transport of sediment,

Recruitment constraints in Singapore's fluted giant clam (Tridacna squamosa) population—A dispersal model approach

“…This seasonal variation, and the two-weekly variations, is well reproduced by the model. It should be noted that the stations Banyan and Sawa are within the Southern Islands area, where large-scale clockwise circulation generates more pronounced eastward currents than in the open Singapore Strait south of the islands [41]. Therefore residual currents within the Southern Islands group in April tend to be directed eastward while in the open strait they may be directed westward.…”

“…The reefs at Raffles Lighthouse experience a larger tidal range due to their proximity to the Singapore Straits [78] and there are no nearby islands to the east, west or south, thus larvae may easily be transported away. Cyrene, on the other hand, is protected by surrounding land masses [41], [80], leading to higher larval retention.…”

“…This model is composed of three domains [41]. The model's outer domain has a grid cell size decreasing from 30 km near the boundaries to ∼300 m around Singapore (see Figure 1).…”

Projected sea level rise and changes in extreme storm surge and wave events during the 21st century in the region of Singapore

“…Regional tides are complex with several amphidromic points located in the South China Sea. Tides propagate into the Singapore Strait via the Malacca Strait and from the open seas to the east, resulting in a complex mix of diurnal and semi-diurnal tides observed around the coastline of Singapore (Maren and Gerritsen, 2012). The mean tidal range at Singapore is ∼ 2 m and the spring maximum range is ∼ 3 m.…”

Larval ecology of the fluted giant clam, Tridacna squamosa, and its potential effects on dispersal models

“…Regardless of the biophysical model type (e.g., Eulerian or Lagrangian), they all typically incorporate a suite of physical and biological parameters (see Erftemeijer et al, 2009;Tay et al, 2012). While the physical parameters largely determine the hydrodynamic transport functions (Huret et al, 2010;van Maren and Gerritsen, 2012), including biological data is also important (as reviewed by Metaxas and Saunders, 2009). Critical factors such as planktonic larval duration (PLD: Shanks, 2009;Gilbert et al, 2010;Wolanski and Kingsford, 2014), timing of gamete or larval release (Edwards et al, 2007;Reitzel et al, 2004), swimming speeds Dekshenieks et al, 1996), diel vertical migration Edwards et al, 2007), mortality rates (Neo et al, 2013), and behaviour Neo et al, 2013) have been included into previous modelling studies for sessile marine invertebrates and fish.…”