Turbulence and Fluxes in the Bottom Boundary Layer (BBL) of Lakes

Vertical exchange driven by turbulent mixing is a key process in lakes. In recent years the ability to measure small scale processes, which is linked to the enormous development of instruments, has led to advances in our understanding of these processes.

Lake Alpnach

Lake Alpnach is 1.5 km wide and 5 km long and is connected to Lake Lucerne by a 3 m deep shelf. The interior dynamics are characterized by wind driven seiching of the first and second vertical mode with a period of about 24 hours and a maximum velocity of 3 cm/s.

The main goal of this project is to compare measurement data from lake Alpnach with a 3-D turbulence model and quantify the water exchange between the bottom boundary layer and the interior as well as the density balance and the buoyancy flux.
Phd research plan

Project objectives:

• Get more insight when and where to apply the eddy correlation method.
  
• Investigate the driving force for turbulent O₂ transport through the BBL and the sediment
• Investigate spatial and temporal structure of the turbulence level (dissipation) of the BBL processes such as bottom convective mixing and shear-induced convection above slopes
• Investigate interaction and communication of buoyancy between interior and BBL water masses (where buoyancy flux is predominant).

Funding: 

• SNF

Collaboration

• Andreas Lorke, University of Constance
• Dr. Lars Umlauf, Baltic Sea Research Institute Warnemünde
• Dr. Peter Berg, University of Virginia

Publications on Lake Alpnach turbulence studies