Impact of Density Gradients on Net Sediment Transport into the Wadden Sea

Burchard, Hans; Flöser, Götz; Staneva, Joanna; Badewien, Thomas H.; Riethmüller, Rolf

doi:10.1175/2007jpo3796.1

Cited by 100 publications

(102 citation statements)

References 59 publications

Supporting

Mentioning

101

Contrasting

Order By: Relevance

“…Residual currents of the estuarine circulation are driven by density gradients that can be caused by (i) horizontal temperature gradients, (ii) differential precipitation, (iii) river discharges and (iv) all possible superpositions. Residual currents of the estuarine circulation flow shorewards in near-bottom waters and offshore in surface waters (Burchard et al, 2008;Flöser et al, 2011). This probably causes a net SPM flux into the Wadden Sea (Burchard et al, 2008(Burchard et al, , 2013.…”

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

“…Residual currents of the estuarine circulation flow shorewards in near-bottom waters and offshore in surface waters (Burchard et al, 2008;Flöser et al, 2011). This probably causes a net SPM flux into the Wadden Sea (Burchard et al, 2008(Burchard et al, , 2013. The Wadden Sea is hypothesized to act as bioreactor, where organic components of SPM become remineralized and are exported in dissolved form (Postma, 1984;Ebenhöh et al, 2004;Grunwald et al, 2010) by the offshore-directed component of the estuarine circulation.…”

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

See 1 more Smart Citation

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

et al. 2016

Self Cite

View full text Add to dashboard Cite

Abstract. Marine coastal ecosystem functioning is crucially linked to the transport and fate of suspended particulate matter (SPM). Transport of SPM is controlled by, amongst other factors, sinking velocity w s . Since the w s of cohesive SPM aggregates varies significantly with size and composition of the mineral and organic origin, w s exhibits large spatial variability along gradients of turbulence, SPM concentration (SPMC) and SPM composition. In this study, we retrieved w s for the German Bight, North Sea, by combining measured vertical turbidity profiles with simulation results for turbulent eddy diffusivity. We analyzed w s with respect to modeled prevailing dissipation rates and found that mean w s were significantly enhanced around log 10 ( (m 2 s −3 )) ≈ −5.5. This region is typically found at water depths of approximately 15 to 20 m along cross-shore transects. Across this zone, SPMC declines towards the offshore waters and a change in particle composition occurs. This characterizes a transition zone with potentially enhanced vertical fluxes. Our findings contribute to the conceptual understanding of nutrient cycling in the coastal region which is as follows. Previous studies identified an estuarine circulation. Its residual landward-oriented bottom currents are loaded with SPM, particularly within the transition zone. This retains and traps fine sediments and particulate-bound nutrients in coastal waters where organic components of SPM become remineralized. Residual surface currents transport dissolved nutrients offshore, where they are again consumed by phytoplankton. Algae excrete extracellular polymeric substances which are known to mediate mineral aggregation and thus sedimentation. This probably takes place particularly in the transition zone and completes the coastal nutrient cycle. The efficiency of the transition zone for retention is thus suggested as an important mechanism that underlies the often observed nutrient gradients towards the coast.

show abstract

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

Section: Implications Of a Cross-coastal Maximum Of Sinking Velocity mentioning

confidence: 99%

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…For freshwater discharge, it is important to remark that in our model it contains no sediment, so freshwater discharge may tend to lower the concentration levels in the domain. However, freshwater enhances estuarine circulation (Burchard et al 2008), so effectively more sediment may be imported. Because of stratification, the near-surface concentration levels may become lower, but the near-bed concentration levels higher.…”

Section: Factor Separation Analysismentioning

confidence: 99%

Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system: the Dutch Wadden Sea

Sassi

Duran‐Matute

Kessel³

et al. 2015

Ocean Dynamics

View full text Add to dashboard Cite

In multiple tidal-inlet systems such as the Dutch Wadden Sea, the exchange of sediments between the coastal lagoon and the adjacent sea is controlled by the combined effect of the tides, wind-driven flows, and densitydriven flows. We investigate the variability of residual (tidally averaged) fluxes of suspended sediment with the three-dimensional numerical model GETM in relation to forcing mechanisms and model parameters. strongly throughout the year, mainly due to wind variability. The net balance between import and export of material is very sensitive to model parameters. Residual fluxes are sensitive to the geographical orientation and location of the inlets, and the effect of driving mechanisms on the residual fluxes and concentrations can be organized hierarchically, with wind forcing having the largest effect on concentration levels and variability.

show abstract

“…The presence of density gradients results in significantly more complex systems. In particular, tidal straining (e.g., Simpson et al, 1990), asymmetry in mixing (e.g., Jay and Musiak, 1994), damping of turbulence by stratification (Geyer, 1993), and longitudinal density gradients (Burchard et al, 2008) have all been…”

Section: *Manuscriptmentioning

confidence: 99%

Modelling-based assessment of suspended sediment dynamics in a hypertidal estuarine channel

et al. 2014

View full text Add to dashboard Cite

We investigate the dynamics of suspended sediment transport in a hypertidal estuarine channel which displays a vertically sheared exchange flow. We apply a three-dimensional process-based model coupling hydrodynamics, turbulence, and sediment transport to the Dee Estuary, in the north-west region of the UK. The numerical model is used to reproduce observations of suspended sediment and to assess physical processes responsible for the observed suspended sediment concentration patterns.The study period focuses on a calm period during which wave-current interactions can reasonably be neglected. Good agreement between model and observations has been obtained. A series of numerical experiments aims to isolate specific processes and confirm that the suspended sediment dynamics result primarily from advection of a longitudinal gradient in concentration during our study period, combined with resuspension and vertical exchange processes. Horizontal advection of sediment presents a strong semidiurnal variability, while vertical exchange processes (including time-varying settling as a proxy for flocculation) exhibit a quarter-diurnal variability. Sediment input from the river is found to have very little importance and spatial gradients in suspended concentration are generated by spatial heterogeneity in bed sediment characteristics and spatial variations in turbulence and bed shear stress.

show abstract

Impact of Density Gradients on Net Sediment Transport into the Wadden Sea

Cited by 100 publications

References 59 publications

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

Maximum sinking velocities of suspended particulate matter in a coastal transition zone

Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system: the Dutch Wadden Sea

Modelling-based assessment of suspended sediment dynamics in a hypertidal estuarine channel

Contact Info

Product

Resources

About