Publication Details

Reference Category Book chapters
DOI / URL link
Title (Primary) Density stratification and stability
Title (Secondary) Encyclopedia of inland waters
Author Boehrer, B.; Schultze, M.;
Publisher Likens, G.E.;
Year 2009
Department SEEFO;
Volume Vol. 1
Language englisch;
Abstract Most lakes show periods of density stratification. The stratification controls currents and vertical circulation, and hence is crucial for understanding and predicting the evolution of water quality in lakes. The availability of nutrients and oxygen, for example, impacts on organisms that can live in the lake. Water properties above the lake bed control recycling of settling material and recycling by bioturbation from buried material in the sediment. Exposure of the lake surface to seasonal changes of weather conditions, inflows and outflows as well as internal chemical transformations create gradients in the distribution of heat and dissolved substances. Both factors contribute to density. Diffusive processes, wind impact on the lake surface, as well as surface cooling and geothermal heating, in general, erode this stratification. In most lakes, mixing overcomes the stratifying processes at times and lakes show circulation periods alternating with stratification periods during an annual cycle. Some lakes, however, can stay permanently stratified. To understand the density stratification, various approaches have been developed to evaluate density at required accuracy. Most usually, temperature and conductivity measurements are used to calculate (potential) density by applying empirical regression curves. In many cases, lake-specific coefficients need to be evaluated. The resulting profiles of stability quantities can be used to estimate vertical transport in a stratified lake. Bulk quantities for the stability indicate the strength of wind forcing that is required for intense upwelling.
ID 72
Persistent UFZ Identifier
Boehrer, B., Schultze, M. (2009):
Density stratification and stability
In: Likens, G.E. (ed.)
Encyclopedia of inland waters
Vol. 1
Elsevier, Amsterdam, p. 583 - 593