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Boehrer, Bertram; Schultze, Martin

doi:10.1002/9783527678488.hbal2005006

Cited by 2 publications

(2 citation statements)

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“…Profiles of temperature ( T ), (in situ) conductivity ( C ), and concentration of dissolved oxygen (O 2 ) from 6 September 2000 in Arendsee, Germany (adapted from Boehrer and Schultze [2005] with permission from ecomed). The boundaries between layers were drawn along gradients in oxygen profiles.…”

Section: Stratification Features Of Heat and Dissolved Substancesmentioning

confidence: 99%

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Stratification of lakes

Boehrer

Schultze

2008

Reviews of Geophysics

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567

381

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Many lakes show 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 in water. The atmosphere imposes a temperature signal on the lake surface. As a result, 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 and removal of gradients of water properties. However, gradients of dissolved substances may be sustained for periods much longer than one annual cycle. Such lakes do not experience full overturns. Gradients may be a consequence of external inflows or groundwater seepage. In addition, photosynthesis at the lake surface and subsequent decomposition of organic material in the deeper layers of a lake can sustain a gradient of dissolved substances. Three more geochemical cycles, namely, calcite precipitation, iron cycle, and manganese cycle, are known for sustaining meromixis. A limited number of lakes do not experience a complete overturn because of pressure dependence of temperature of maximum density. Such lakes must be sufficiently deep and lie in the appropriate climate zone. Although these lakes are permanently stratified, deep waters are well ventilated, and chemical differences are small. Turbulent mixing and convective deep water renewal must be very effective. As a consequence, these lakes usually are not termed meromictic. Permanent stratification may also be created by episodic partial recharging of the deep water layer. This mechanism resembles the cycling of the ocean: horizontal gradients result from gradients at the surface, such as differential cooling or enhanced evaporation in adjacent shallow side bays. Dense water parcels can be formed which intrude the deep water layer. In the final section, stratification relevant physical properties, such as sound speed, hydrostatic pressure, electrical conductivity, and density, are discussed. The assumptions behind salinity, electrical conductance, potential density, and potential temperature are introduced. Finally, empirical and theoretical approaches for quantitative evaluation from easy to measure properties conclude this contribution.

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Section: Stratification Features Of Heat and Dissolved Substancesmentioning

confidence: 99%

“…Profiles of temperature, conductance, density, and dissolved oxygen from Rassnitzer See in former mining area Merseburg‐Ost on 7 October 2003 (adapted from Boehrer and Schultze [2005] with permission from ecomed). (Oxygen concentration numerically corrected for response time of 7.5 s of the sensor).…”

Section: Meromixis: Permanent Stratificationmentioning

confidence: 99%