A local eddy viscosity parameterization for wind-driven estuarine exchange flow, Part II

A local eddy viscosity parameterization for wind-driven estuarine exchange flow, Part II: Entrainment

Basdurak, N. Berkay (Leibniz Institute for Baltic Sea Research Warnemünde; Middle East Technical University)
Burchard, Hans (Leibniz Institute for Baltic Sea Research Warnemünde)
Schuttelaars, H.M. (TU Delft Mathematical Physics)

2023

Structure and intensity of estuarine exchange flow depend significantly on the eddy viscosity A_v profile which is dynamically linked to various forces (e.g., gravitational, tidal, wind-driven). The impact of winds on the exchange flow is complex due to its direct (local and remote changes in shear and density stratification) and indirect (modifications to A_v profiles) contributions. This study aims (i) to include wind entrainment effects in the tidally averaged A_v parameterization; (ii) to develop an analytical one-dimensional model for the wind driven exchange flow by using this novel parameterization and assess the tidally averaged dynamics over a relevant physical parameter-space, subdomains of which have not yet been explored numerically. This one-dimensional model is based on a balance between frictional forces and pressure gradient, calibrated with a tidally-resolving one-dimensional water-column model with second-moment closure. Structure and intensity of the resulting exchange flow profiles are analyzed with respect to three dimensionless parameters (the unsteadiness of boundary layer mixing U_n, scaled-directional wind stress W, and horizontal stratification S_i). While down-estuarine winds enhance the gravitational circulation, up-estuarine winds result in either a two-layer inverted circulation opposing the gravitational circulation, or a three-layer flow (favored by relatively strong S_i, weak W, and moderate U_n) that is up-estuarine at the surface with classical two-layer circulation underneath. Relative thickness of surface and bottom boundary layers affect both the intensity and the inflection depth of the exchange flow layers. Up-estuarine winds with W≳0.5 yield unstable stratification and reduce the exchange flow intensity with increasing W.

Analytical techniques
Boundary layer mixing
Eddy viscosity parameterization
Estuarine dynamics
Wind driven exchange flow
Wind entrainment

http://resolver.tudelft.nl/uuid:cfde0bc3-9d00-4634-b59f-8756bbed8901

https://doi.org/10.1016/j.pocean.2023.103166

2024-05-08

0079-6611

Progress in Oceanography, 219

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

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journal article

© 2023 N. Berkay Basdurak, Hans Burchard, H.M. Schuttelaars