the dynamics of turbidity zones in tidal estuaries · 2009. 1. 27. · the dynamics of turbidity...
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The dynamics of turbidity zones intidal estuaries
Hans Burchard
�
and Manuel Ruiz Villarreal
�
1. Baltic Sea Research Institute Warnemunde, Germany2. Institute for Oceanography, University of Hamburg,
Germany
GHAMES-Seminar in Liege, June 13, 2002 – p.1/19
Program of the talk
� Phenomenology
� Conceptual models
� Numerical simulations (historical)
� Numerical simulations (recent)
� Conclusions
GHAMES-Seminar in Liege, June 13, 2002 – p.2/19
Map of the tidal Elbe
9°00' 10' 20' 30' 40' 50' 50' 40' 30' 10°00'
54°00'
53°30' 0 10km
53°40'
53°50'
20' 8°10'
54°10'
Scharhörn
Gr. Knechtsand
Neuwerk
Cuxhaven
Friedrichskoog
Oste
Nord-
Ost
see-
Kana
l
Stör
Wischh. Süderelbe
Schwinge
Krückau
Pinnau
Este
Lühe
Med
em
Brunsbüttel
Glückstadt
Stade
Hamburg 630
640 650
660
670
680
690
700
710 720
730
740
Strom-km 700
Trischen
Watt
WGE Be 10.96
Mühlen- berger Loch
Pagensand
Medemgrund
Neufelder Sand
Großer Vogelsand
Medemsand
Gelbsand
GHAMES-Seminar in Liege, June 13, 2002 – p.3/19
PhenomenologySPM observations in the tidal Elbe
Pers. comm. Jens Kappenberg
GHAMES-Seminar in Liege, June 13, 2002 – p.4/19
PhenomenologySPM observations in the tidal Elbe
Pers. comm. Jens Kappenberg
GHAMES-Seminar in Liege, June 13, 2002 – p.5/19
PhenomenologySPM observations in Columbia River
Salinity
SPM
Pers. comm. David Jay, Phillip Orton
GHAMES-Seminar in Liege, June 13, 2002 – p.6/19
Classical conceptual models
� Flocculation of riverine colloids due to the ioncontent of the saline sea water (Lucht [1953]).
� "The peculiar process of mixing between riverineand marine water in the tidal zone works as aSPM trap." (Postma und Kalle [1955]).
Schoellhamer & Burau, 1998
GHAMES-Seminar in Liege, June 13, 2002 – p.7/19
Classical conceptual modelsDensity currents from numerical lock exchange
� � �
h
-15
-10
-5
10 20 30 40 50 600
1
2
3
4
5
x / km
z / m
PSfrag replacements
��� / kg m � �
GHAMES-Seminar in Liege, June 13, 2002 – p.8/19
Conceptual model
Jay & Musiak, 1994
GHAMES-Seminar in Liege, June 13, 2002 – p.9/19
Computer simulations
Burchard & Baumert, 1998
GHAMES-Seminar in Liege, June 13, 2002 – p.10/19
Computer simulations
Burchard & Baumert, 1998
GHAMES-Seminar in Liege, June 13, 2002 – p.11/19
Computer simulations
Burchard & Baumert, 1998
GHAMES-Seminar in Liege, June 13, 2002 – p.12/19
GETM
� Three dimensional, hydrostatic, free surface, baroclinic
� Mode-splitting, Arakawa-C grid
� Horizontal coord.: Cartesian, spherical or orthogonal
� Vertical coord.: Sigma, z-levels or generalized
� Turbulence closures from GOTM (http://www.gotm.net)
� Various advection schemes for momentum and tracers
� Stable drying and flooding algorithm
Burchard & Bolding, 2002
GHAMES-Seminar in Liege, June 13, 2002 – p.13/19
Suspended matter moduleTransport equation:
��
� � ��� ��� � � � �� �� � � � ��� � ��� � � � � � �� ��� ��
��� � � � �
(1)
Bottom boundary condition:
� � � � ��
�� � � ��� � � (2)
Erosion & sedimentation flux:
��� � � ����
���� �� � � � � �! � � � � � � �� � �
���� �� � � � �#" (3)
Bottom SPM pool: ��
�$ � � � � �%� (4)
GHAMES-Seminar in Liege, June 13, 2002 – p.14/19
Two-dimensional experiments
� Salinity and SPM (click for animation), noadvection of turbulence
�
Salinity and eddy diffusivity (click for animation),no advection of turbulence
�
Salinity and eddy diffusivity (click for animation),with advection of turbulence
GHAMES-Seminar in Liege, June 13, 2002 – p.15/19
Idealised bathymetry
GHAMES-Seminar in Liege, June 13, 2002 – p.16/19
Three-dimensional experiment
� Salinity and SPM, longitudinal section (click foranimation)
� Salinity, SPM and velocity, surface view (clickfor animation)
� Salinity and velocity, cross-sectional view (clickfor animation)
GHAMES-Seminar in Liege, June 13, 2002 – p.17/19
Conclusions
� In many estuaries, turbidity maxima (ETMs) areobserved at the tip of the salt intrusion.
� These types of ETMs have been numericallysimulated with different 2D- and 3D-models.
� Two major ETM generation mechanisms havebeen pinpointed, residual gravitational circulationand tidal velocity asymmetry.
� Even in idealised 3D cases, complex secondaryflows occur and strongly influence the ETMdynamics.
GHAMES-Seminar in Liege, June 13, 2002 – p.18/19
Future work
� Detailed numerical analysis of ETM dynamics inthree dimensions.
� Numerical analysis of turbulence advection.
� Application of the model to process studies in thetidal Elbe by using a curvi-linear orthogonal grid.
GHAMES-Seminar in Liege, June 13, 2002 – p.19/19