The dynamics of turbidity zones in tidal estuaries ¡
Hans Burchard and Manuel Ruiz Villarreal [email protected].
1. Baltic Sea Research Institute Warnemunde,¨ Germany 2. 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
54°10'
WGE Be 10.96
Trischen
Großer Vogelsand Friedrichskoog Gelbsand 54°00'
740
Scharhörn 730 Nord-Ostsee-Kanal Neufelder Brunsbüttel Stör Sand Neuwerk Medemsand 700 720 710 690 Cuxhaven 53°50' Gr. Knechtsand Medemgrund 680
Medem Glückstadt
Wischh. Süderelbe 670
Krückau
Oste Pagensand Pinnau 660 53°40'
Stade
650 640 Watt 630 Hamburg Schwinge
Strom-km 700 Lühe Mühlen- berger Loch 0 10km 53°30' Este
8°10' 20' 30' 40' 50' 9°00' 10' 20' 30' 40' 50' 10°00'
GHAMES-Seminar in Liege,` June 13, 2002 – p.3/19 Phenomenology SPM observations in the tidal Elbe
Pers. comm. Jens Kappenberg
GHAMES-Seminar in Liege,` June 13, 2002 – p.4/19 Phenomenology SPM observations in the tidal Elbe
Pers. comm. Jens Kappenberg
GHAMES-Seminar in Liege,` June 13, 2002 – p.5/19 Phenomenology SPM 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 ion content of the saline sea water (Lucht [1953]).
"The peculiar process of mixing between riverine and marine water in the tidal zone works as a SPM trap." (Postma und Kalle [1955]).
Schoellhamer & Burau, 1998
GHAMES-Seminar in Liege,` June 13, 2002 – p.7/19 Classical conceptual models Density currents from numerical lock exchange ¢
¡ h § ¦ £¥¤ / kg m 5
-5 4 3 -10
z / m 2
-15 1
0 PSfrag replacements 10 20 30 40 50 60 x / km
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 module Transport 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), no advection 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 for animation)
Salinity, SPM and velocity, surface view (click for animation)
Salinity and velocity, cross-sectional view (click for animation)
GHAMES-Seminar in Liege,` June 13, 2002 – p.17/19 Conclusions
In many estuaries, turbidity maxima (ETMs) are observed at the tip of the salt intrusion.
These types of ETMs have been numerically simulated with different 2D- and 3D-models.
Two major ETM generation mechanisms have been pinpointed, residual gravitational circulation and tidal velocity asymmetry.
Even in idealised 3D cases, complex secondary ¯ows occur and strongly in¯uence the ETM dynamics.
GHAMES-Seminar in Liege,` June 13, 2002 – p.18/19 Future work
Detailed numerical analysis of ETM dynamics in three dimensions.
Numerical analysis of turbulence advection.
Application of the model to process studies in the tidal Elbe by using a curvi-linear orthogonal grid.
GHAMES-Seminar in Liege,` June 13, 2002 – p.19/19