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Strong bottom currents in large, deep Lake Geneva generated by higher vertical-mode Poincaré waves.
Rafael Sebastian Reiss1,2, Ulrich Lemmin1, Claire Monin1,3
1Ecological Engineering Laboratory (ECOL), Institute of Environmental Engineering (IIE), Faculty of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
Communications Earth & Environment
|September 6, 2024
Summary
Higher vertical-mode Poincaré waves in deep lakes like Lake Geneva create strong bottom currents. Weak stratification significantly alters wave patterns, impacting deepwater mixing and sediment exchange.
Area of Science:
- Geophysics
- Physical Limnology
Background:
- Internal seiches are common in large lakes.
- The impact of higher vertical-mode seiches on deepwater dynamics is poorly understood.
Purpose of the Study:
- To investigate the influence of higher vertical-mode Poincaré waves on deepwater dynamics in Lake Geneva.
- To analyze the effects of stratification on these wave structures.
Main Methods:
- Combined summer-long current and temperature observations.
- Utilized 3D numerical modeling.
Main Results:
- Detected previously unknown vertical mode-two and mode-three Poincaré waves.
- Observed bottom-boundary layer currents up to 4 cm/s.
- Identified three simultaneously excited Poincaré wave amphidromic cells.
- Found that weak stratification shifted the lower vertical node to deeper levels, enhancing bottom currents.
Conclusions:
- Higher vertical-mode Poincaré waves significantly impact deepwater dynamics in lakes.
- Stratification plays a crucial role in modifying wave structure and enhancing bottom currents.
- Classical models are insufficient for characterizing these phenomena in deep lakes.
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