Simulating tropical river plumes, a set of parametrizations based on macroscale data: A test case in the Mekong Delta region

Hordoir, Robinson; Nguyen, Kim Dan; Polcher, Jan

doi:10.1029/2005jc003392

Cited by 22 publications

(21 citation statements)

References 43 publications

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“…However, the plume never extends further than 20 km from the coast, which is the limit of the subaqueous delta. Our results are consistent with those from Hordoir et al [33], who showed that the plume of the Mekong River is dominated by geostrophy from a dynamical perspective, with freshwater advected by a coastally trapped baroclinic current. This behavior was confirmed by a Rossby number less than 1 throughout the year, due to the large freshwater discharge.…”

Section: Discussionsupporting

confidence: 83%

“…Southern estuaries in the case of SW waves in the low flow season (Figure 3f) and in the case of Southern waves in the flood season (Figure 4e). Globally, the river plume is very narrow and its extent is reduced throughout the year (as also shown by Loisel et al [25]) for two reasons: (1) most of the particles carried by the river settle in the lower estuary or around the river mouths; (2) the plume is constrained along a baroclinic coastal current as demonstrated by Hordoir et al [33]. Differences between low flow and flood seasons are small because the turbidity patterns are driven by wave action, more than by the river flow.…”

Section: Temporal Variation Of Sscmentioning

confidence: 85%

“…The continental shelf is very shallow (most of the plume flows over depths <10-15 m), the river mouths being located in a sedimental plain. Despite the low Coriolis number, the large freshwater discharge still creates a baroclinic coastal current flowing in the direction of the Kelvin wave [33].…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulations of Suspended Sediment Dynamics Due to Seasonal Forcing in the Mekong Coastal Area

Vinh¹,

Ouillon

Thao³

et al. 2016

Water

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Abstract:The Mekong River is ranked as the 8th in terms of water discharge and as the 10th in terms of sediment load in the world. During the last 4500 years, its delta prograded more than 250 km to the south due to a tremendous amount of sediments deposited, and turned from a "tide-dominated" delta into a "wave-and-tide dominated" delta. This study aims at completing our knowledge on the fate of sediments that may be stored in estuarine or coastal systems, or dispersed over the continental shelf and slope. Sediment transport in the Mekong River Delta (MRD) coastal area was studied by numerical simulations using the Delft3D model. The model configuration was calibrated and validated from data collected in situ during 4 periods from 2012 to 2014. Then, 50 scenarios corresponding to different wave conditions (derived from the wave climate) and river discharge values typical of low flow and flood seasons enabled us to quantify the dispersal patterns of fluvial sediments close to the mouths and along the coast. Sediments mostly settled in the estuary and close to the mouths under calm conditions, and suspended sediment with higher concentrations extend further offshore with higher waves. Waves from the Southeast enhanced the concentration all along the MRD coastal zone. Waves from the South and Southwest induced coastal erosion, higher suspended sediment concentrations in front of the southern delta, and a net transport towards the Northeast of the delta. Because of episodes of Southern and Southwestern waves during the low flow season, the net alongshore suspended sediment transport is oriented Northeastward and decreases from the Southwestern part of the coastal zone (~960ˆ10 3 t yr´1) to the Northeastern part (~650ˆ10 3 t yr´1).

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Section: Discussionsupporting

confidence: 83%

Section: Temporal Variation Of Sscmentioning

confidence: 85%

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Numerical Simulations of Suspended Sediment Dynamics Due to Seasonal Forcing in the Mekong Coastal Area

Vinh¹,

Ouillon

Thao³

et al. 2016

Water

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“…Thus, the wind‐driven circulation of freshwater is not affected by any increase of the stratification and extends over the entire mixed layer which explains the low advection velocities. If the release of freshwater occurs in a sea with higher salinity, the current structure will, on shorter time scales, be affected by the presence of juvenile freshwater [ Fong and Geyer , 2001; Hordoir et al , 2006]. During the advection in the Baltic proper, freshwater can be considered as a passive tracer providing information on the variability of the large‐scale circulation.…”

Section: Resultsmentioning

confidence: 99%

Freshwater fluxes in the Baltic Sea: A model study

Hordoir¹,

Meier²

2010

J. Geophys. Res.

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The dynamics of “juvenile” freshwater, which is released during spring into the Baltic proper, is studied using a numerical three‐dimensional circulation model. Two methods are used. First, freshwater heights are calculated using simulated salinity fields, and their seasonal variability is analyzed. When compared to climatological observations, the model represents the seasonal variability of freshwater heights well. However, the method does not allow a proper study of the dynamics of juvenile freshwater fluxes. Consequently, a second method is used where a passive tracer, which marks freshwater, is utilized. This method provides a better description of the seasonal spreading of juvenile freshwater in the Baltic proper, although further investigations are still necessary to trace juvenile freshwater. The results from this second method show that juvenile freshwater does not reach the center of the Baltic proper before late summer. During one season, only a small amount of juvenile freshwater may reach the entrance of the Baltic Sea. The increased vertical stratification generated by the arrival of juvenile freshwater and the subsequent baroclinic adjustment may trigger the onset of the spring bloom in accordance to earlier suggestions. Further, the seasonal cycle and inter‐annual variability of the freshwater outflow from the Baltic Sea are studied. Seasonal changes of the freshwater outflow are closely connected with that of the zonal wind, although the annual mean outflow is given by the total runoff into the Baltic Sea. Thus, the inter‐annual variability of the seasonal freshwater outflow maximum is highly correlated with the North Atlantic Oscillation.

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“…Zu et al (2014) pointed out that wind determines the horizontal shape and spreading of the plume by wind-driven coastal currents. Winds and ambient wind-driven current play important roles in transporting the freshwater downstream (Dong et al, 2004;Fong & Geyer, 2002;Gan et al, 2009;Hordoir et al, 2006). For instance, a study of Merrimack River plume by Kakoulaki et al (2014) shows that the plumes with scales less than 12 km are sensitive to wind direction when wind speed exceeds 4 m/s.…”

Section: River Plumesmentioning

confidence: 99%

Numerical Experiments on Variation of Freshwater Plume and Leakage Effect From Mississippi River Diversion in the Lake Pontchartrain Estuary

Huang

White

et al. 2020

JGR Oceans

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A Finite Volume Community Ocean Model is used to investigate how wind impacts the circulation and evolution of a freshwater plume from Mississippi River diversion in the Lake Pontchartrain Estuary. Results show that northerly and southerly winds tend to stretch the plume in the east‐west directions, while easterly and westerly winds constrain the plume in the north‐south directions. Increasing wind magnitude tends to increase the total salt content of the estuary except under weak westerly wind (<6 m/s) during which salt content decreases. A no‐motion middepth interface is found (by the model and verified by the data), separating the top layer downwind flow and bottom layer upwind flow. Increasing wind magnitude can enhance the two‐layered flows and lower the no‐motion plane between the two opposite flows. Apparent small leakage of the river water through the diversion structure prior to its opening is found to impact the vertical structure of flows and salinity: Mixing is facilitated by the large amount of freshwater leaked into the lake prior to the opening of the diversion; wind‐driven gyres are diminished; the average potential energy demand, a quantity used to measure the vertical stratification, is reduced to very low values; more deviation from the quasi‐steady state balance tends to occur; and a total of 3.7 × 108 kg of salt is reduced during the opening period of the Bonnet Carré Spillway. The Lake Pontchartrain Estuary is completely dominated by the river water within about 25 days, when salinity drops from an average value of 4 g/kg to essentially zero.

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Simulating tropical river plumes, a set of parametrizations based on macroscale data: A test case in the Mekong Delta region

Cited by 22 publications

References 43 publications

Numerical Simulations of Suspended Sediment Dynamics Due to Seasonal Forcing in the Mekong Coastal Area

Numerical Simulations of Suspended Sediment Dynamics Due to Seasonal Forcing in the Mekong Coastal Area

Freshwater fluxes in the Baltic Sea: A model study

Numerical Experiments on Variation of Freshwater Plume and Leakage Effect From Mississippi River Diversion in the Lake Pontchartrain Estuary

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