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| Titel |
Effects of climate change on deep-water oxygen and winter mixing in a deep lake (Lake Geneva) |
| VerfasserIn |
Robert Schwefel, Alfred Wüest, Damien Bouffard |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124700
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| Publikation (Nr.) |
 EGU/EGU2016-4177.pdf |
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| Zusammenfassung |
| Oxygen is the most important dissolved gas for lake ecosystems. Because low oxygen
concentrations are an ongoing problem in many parts of the oceans and numerous lakes,
oxygen depletion processes have been intensively studied over the last decades and
were mainly attributed to high nutrient loads. Recently, climate-induced changes in
stratification and mixing behavior were recognized as additional thread to hypolimnetic
oxygen budgets in lakes and reservoirs [Matzinger et al., 2007; Zhang et al., 2015].
Observational data of Lake Geneva, a deep perialpine lake situated between France and
Switzerland showed no decreasing trend in hypoxia over the last 43 years, despite an
impressive reduction in nutrient input during this period. Instead, hypoxic conditions
were predominantly controlled by deep mixing end of winter and in turn by winter
temperatures. To test the sensitivity of Lake Geneva on future climate change and changes
in water transparency, we simulated the hydrodynamics and temperature of Lake
Geneva under varying conditions for atmospheric temperature and water clarity
performed with the one-dimensional model SIMSTRAT [Goudsmit, 2002]. The results
show, that the stratification in lakes is only weakly affected by changes in light
absorption due to varying water quality. For conditions expected for the end of
the century, a decrease in the annual mean deep convective mixing of up to 45 m
is predicted. Also complete mixing events over the whole lake are less likely to
occur. A change in the hypolimnetic oxygen concentration of up to 20% can thus be
expected in the future. These results show, that changes in deep mixing have an
equally strong impact as eutrophication on the deep-water oxygen development of
oligomictic lakes and have to be considered in the prediction of the future development of
lakes.
References:
Goudsmit, G. H., H. Burchard, F. Peeters, and A. Wüest (2002), Application of k-ε turbulence
models to enclosed basins: The role of internal seiches, J. Geophys. Res., 107(C12),
3230.
Matzinger, A., M. Schmid, E. Veljanoska-Sarafiloska, S. Patceva, D. Guseska, B. Wagner, B.
Müller, M. Sturm, and A. Wüest (2007), Eutrophication of ancient Lake Ohrid: Global
warming amplifies detrimental effects of increased nutrient inputs, Limnol. Oceanogr., 52(1),
338–353.
Zhang, Y., Z. Wu, M. Liu, J. He, K. Shi, Y. Zhou, M. Wang, and X. Liu (2015), Dissolved
oxygen stratification and response to thermal structure and long-term climate change in a
large and deep subtropical reservoir (Lake Qiandaohu, China), Water Res., 75,
249–258. |
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