Effect of lake level rise on vertical transport and mixing processes in Lake Van (Turkey)
Zusammenfassung der Projektergebnisse
In saline Lake Van a lake level rise is associated with a significant reduction in deep water renewal and oxygenation. During rising water levels the occurrence of density plumes transporting water with near surface properties along the lake boundaries to largest depth is reduced due to the increase in salinity gradients. The kinetic energy in the deep water required for turbulent mixing in Lake Van is mainly associated with internal Poincare-type waves. Because of density stratification due to salinity gradients these waves occur not only during the summer period in connection with thermal stratification, but also during the winter time. Numerical modelling of transient tracers suggests that in Lake Van the residence fime in the deep water below 400 m was about 5 yr in 1988 and increased after lake level rise by 12 years within 17 yr reaching an isolation age in the deep water of 17 yr in 2005. Our investigations from Lake Van indicate that in deep saline lakes even small changes in the hydrological regime can have a large impact on deep-water renewal and also on the biogeochemical conditions. The lake level increase by 2 meters in Lake Van reduced deep-water exchange sufficiendy that a more than 100 m thick deep-water body became anoxic within a 10 yr time period. Furthermore, the data suggest that the consequences associated with a lake level increase may prevail substanfially longer than the increase itself, i.e. the anoxic conditions in the deep water were sfill present 10 yr after the maximum lake level was reached and 3 yr after the level was back at the level of 1989. Hence, regularly re-occurring small level rises by a few meters or substantially larger lake level rises occurring slowly but over extend periods of time (see Landmann et al. 1996; Wick et al. 2003) may have severe consequences for deep-water renewal and for the entire ecosystem that should be reflected in sediment records and must be taken into account when interpreting lake-borne proxies.
Projektbezogene Publikationen (Auswahl)
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Mischungsprozesse im Van See (Türkei). Lake Constance - Physicists - Workshop, Konstanz, 14.10.2005
Kaden, H., Peeters, F., Lorke, A., Kipfer, R., Brennwald, M., Tomonaga, Y., Gökdere, F.
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Mixing Processes in Lake Van (Turkey). 9th European Workshop on Physical Processes in Natural Waters, Lancaster, UK, 4.- 6.09.2005
Kaden, H., Peeters, F., Lorke, A., Kipfer, R., Brennwald, M., Tomonaga, Y.
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Mischungsprozesse im Van See (Türkei) - Ein Fortschrittsbericht. German Society of Physics - Environmental Physics, Heidelberg, 13.-15.03.2006
Kaden, H., Peeters, F., Kipfer, R., Tomonaga, Y.
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Some Remarks on Lake Van with a View to Lake Level Fluctuations & Climate Change, and Tectonics / Volcanology & Mantel Fluids. PaleoVan workshop, Van, Turkey, 6.-9.06.2006
Brennwald, M., Kaden, H., Karabiyikoglu, M., Kipfer, R., Orcen, S., Peeters, F., Tomanaga,Y.
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Auswirkung von Seespiegeländerungeni auf die Tiefenwassererneuerung im Van See (Türkei). German Society of Limnology, Konstanz, 22.-26.09.2008
Kaden, H., Peeters, F., Lorke, A., Kipfer, R., Tomonaga, Y.
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Impact of lake level changes on deep-water renewal and oxic conditions in a large saline lake (Lake Van, Turkey). ASLO. Nice, France, 25. - 30.01.2009. poster presentation
Kaden, H., Lorke, A., Kipfer, R., Tomonaga, Y., Peeters, F.
