- 1Faculty of Geoscience and Environment, Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland (tomy.doda@unil.ch)
- 2Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters–Research and Management, Kastanienbaum, Switzerland
- 3Tahoe Environmental Research Center, University of California, Davis, Davis, California, USA
- 4Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
Lakes with multiple basins exhibit spatially variable biogeochemical and physical properties. In these systems, wind- and convection-driven inter-basin exchange facilitates the transport of heat and solutes between basins, contributing to both surface and deepwater renewal. Such exchanges may supply oxygen to the deep, anoxic waters of oligomictic lakes, in addition to winter vertical mixing. As a result, oxygen mass budgets require estimates of the horizontal and vertical turbulent fluxes generated by exchange flows. Yet, the spatial variability of turbulent mixing across lake basins and the turbulent signature of inter-basin exchange remain poorly understood. This study investigates these processes in Lake Zug, Switzerland (surface area of 38 km², mean depth of 83 m, maximal depth of 197 m), a two-basin oligomictic lake. The lake is divided into a shallow, well-ventilated North basin and a deep, redox-stratified South basin, separated by a one-kilometer-wide constriction. The zonation of redox processes in Lake Zug is governed by the sources and sinks of oxygen, necessitating the quantification of turbulent transport by exchange flows. We deployed three moorings equipped with a vertical array of thermistors, oxygen loggers and acoustic Doppler current profilers (ADCPs) for one year along the constriction, allowing us to characterize the nature and dynamics of exchange flows. Additionally, conductivity-temperature-depth (CTD) and microstructure profiles were collected along North-South transects with a VMP-500 free-falling profiler (Rockland Scientific International Inc.). We quantified the spatial variability of turbulent mixing by estimating Thorpe displacements (LT), turbulent kinetic energy dissipation rate (ε), and vertical turbulent diffusivity (Kz) from the microstructure data. These observations provide new insight into the effects of inter-basin exchange flows on the spatial heterogeneity of turbulence, improving our understanding of multi-basin lake physics and biogeochemistry.
How to cite: Doda, T., Rama, J., Sepúlveda Steiner, O., N. Ulloa, H., Janssen, D., and Bouffard, D.: Spatial variability of turbulent mixing across the constriction of a two-basin lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12590, https://doi.org/10.5194/egusphere-egu25-12590, 2025.
