Stratification features in lakes: temperature stratification, meromixis, and thermobaric stratification
Event details
| Date | 15.10.2013 |
| Hour | 16:15 › 17:15 |
| Speaker | Prof. Bertram Boehrer, Helmholtz Centre for Environmental Research - UFZ, Limnophysics, Magdeburg (DE) |
| Location | |
| Category | Conferences - Seminars |
Abstract:
Many lakes show a vertical stratification of their water masses at least for some extended time periods. Density differences in water bodies facilitate an evolution of chemical differences with many consequences for living organisms in lakes. Temperature and dissolved substances contribute to density differences. Thermal stratification can be established during the warm season, if a lake is sufficiently deep. On the contrary, during the cold period, surface cooling forces vertical circulation of water masses.
However, gradients of dissolved substances may be sustained for periods much longer than one annual cycle. Such lakes do not experience full overturns. Photosynthesis in the upper water body and subsequent decomposition of organic material in the deeper layers of a lake can sustain a gradient of dissolved substances. Three more biogeochemical cycles, namely, calcite precipitation, iron cycle, and manganese cycle, are known for sustaining meromixis. The presentation will close with some examples of thermobaric stratification, i.e. the rare case where pressure effects control the thermal stratification of freshwater lakes.
Dr Bertram Boehrer leads the Limnophysics Group at the Helmholtz Centre for Environmental Research – UFZ in Magdeburg (Germany). He also teaches at the Faculty for Physics and Astronomy at the University of Heidelberg (Germany). He is physicist by training and has graduated with a master’s thesis from the University of Heidelberg on the internal waves in Lake Constance and a PhD thesis from The Univ. of Western Australia on convection. In the 1990s and early 2000s, he had dedicated his work to the pressing environmental concerns of lakes coming into existence in open pit mines of former East Germany. Recent scientific publications comprise quantifications of lake stratification such as thermobaric effects, meromixis, consequences of chemical transformations and global change for the stratification and deep recirculation of lakes.
Many lakes show a vertical stratification of their water masses at least for some extended time periods. Density differences in water bodies facilitate an evolution of chemical differences with many consequences for living organisms in lakes. Temperature and dissolved substances contribute to density differences. Thermal stratification can be established during the warm season, if a lake is sufficiently deep. On the contrary, during the cold period, surface cooling forces vertical circulation of water masses.
However, gradients of dissolved substances may be sustained for periods much longer than one annual cycle. Such lakes do not experience full overturns. Photosynthesis in the upper water body and subsequent decomposition of organic material in the deeper layers of a lake can sustain a gradient of dissolved substances. Three more biogeochemical cycles, namely, calcite precipitation, iron cycle, and manganese cycle, are known for sustaining meromixis. The presentation will close with some examples of thermobaric stratification, i.e. the rare case where pressure effects control the thermal stratification of freshwater lakes.
Dr Bertram Boehrer leads the Limnophysics Group at the Helmholtz Centre for Environmental Research – UFZ in Magdeburg (Germany). He also teaches at the Faculty for Physics and Astronomy at the University of Heidelberg (Germany). He is physicist by training and has graduated with a master’s thesis from the University of Heidelberg on the internal waves in Lake Constance and a PhD thesis from The Univ. of Western Australia on convection. In the 1990s and early 2000s, he had dedicated his work to the pressing environmental concerns of lakes coming into existence in open pit mines of former East Germany. Recent scientific publications comprise quantifications of lake stratification such as thermobaric effects, meromixis, consequences of chemical transformations and global change for the stratification and deep recirculation of lakes.
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. D. Andrew Barry, ECOL