Mixing and exchange processes between two estuaries in Stockholm Archipelago, Sweden
2008 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015Article in journal (Other academic) Submitted
ECOM, a three-dimensional time dependant hydrodynamic and thermodynamic model, was used to investigate the mixing and exchange processes between Farstaviken and Baggensfjärden estu-aries in Stockholm archipelago during April to November 1997. Possible causes of bottom oxy-gen deficiency in the smaller estuary of Farstaviken were also investigated. The model with an additional boundary condition for the sediment-water heat exchange and modifications to reduce the pressure gradient error successfully produced the observed temperature profiles by allowing a time variable reduction in the magnitude of the observed wind speed. In Farstaviken (during stratification periods) the epilimnion region occupies 2.5%-17.5% of the flow depth. The ex-change process between the two smaller and larger estuaries is different from that observed be-tween larger basins where density driven currents dominate. Here, the process is primarily con-trolled by wind action and tides. On average 5% of the total water volume of Farstaviken is exchanged with Baggensfjärden on daily basis. The bottom oxygen deficiency in Farstaviken during April to November 1997 is partially related to the topography of the basin and the wind sheltering effect. To investigate this issue as well as the sensitivity of mixing to the changes in topography, additional simulations were performed using a modified bathymetry. The original bathymetry was smoothed using the 2D Gaussian filter. The results showed that both the intensi-ties and penetration depths of eddies were increased in comparison with the original bathymetry. The enhanced circulation can also contribute to increase the content of dissolved oxygen near the bottom of Farstaviken.
Place, publisher, year, edition, pages
Mixing and flow exchange, Three-dimensional modeling, Wind sheltering, Basin bathymetry, Bottom oxygen deficiency
IdentifiersURN: urn:nbn:se:kth:diva-8248OAI: oai:DiVA.org:kth-8248DiVA: diva2:13519
QS 201203152008-04-222008-04-222012-03-15Bibliographically approved