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 p.14/19 (1) (2) (3) (4) – 2002 13, ¨#" ¨ June ¡ ` ege, Li ¤ in ¥§ ¥ ¡ GHAMES-Seminar ¨ ¡ % ¨ ¡ module ¥§ ¥ ¨ ¤ ! ¢ ¥ $ ¨ flux: ¡ ¨ ¡ ¥§ ¤© matter condition: ¢ ¥ ¨ ¡ pool: ¥§¦ sedimentation equation: ¤£ & boundary SPM ¢ ¡ ransport T Bottom Erosion Bottom Suspended 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.