Thermobaricity: Pressure effects on temperature stratification and circulation in lakes - PONTEM

• Applicants: Privatdozent Dr. Bertram Boehrer; Professor Dr. Thomas Richter
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Mathematics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524611035

Societal Relevance: Providing the population with sufficient good quality water will be one of the great challenges in near future. Land use and climate change exacerbate this problem. We have only limited possibilities to create new water or transfer water in reservoirs seasonally to periods of shortage. Wise use and management of water resources appear as the most promising tools to alleviate the situation. Hence, numerical models have been adopted for lakes: the implementation of water properties however is still tied to ocean assumptions. As a consequence, simulated flows in the deep water of lakes close to temperature of maximum density (i.e. near 4°C) are flawed or entirely disconnected from reality. We hypothesize that an inclusion of thermobaricity in numerical models solves this issue and thermobaric effects are properly reflected. We have much better knowledge of the physical properties of lake waters. Numerical lake models could be substantially improved. Scientific Challenge: Thermobaricity is controlling recirculation in deep lakes in the temperate and subpolar climate zone. Though the topic has gained interest recently in oceanography, the features in deep lakes have not been properly dealt with. By definition, the convenient property of potential density is lost, when thermobaric effects are dominant. This makes stability considerations difficult to display. However, we are convinced that the description of thermobaric effects can significantly be improved. We propose to start from basics of thermodynamic approaches to stability considerations to parsimonious modelling and will complete this research programme by the implementation of a proper inclusion of thermobaricity in numerical models to demonstrate the effects in some prominent cases. We are convinced that with our joined competences we find new approaches to understand and communicate thermobaric effects. From our experience we find effective numerical approaches to properly deal with the topic to implement and demonstrate thermobaric effects in some deep lakes. We will use the model DELFT3D by DELTARES for numerical simulations. We expect that this project opens the perspective of future fruitful collaboration.

• DFG Programme: Research Grants