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Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers: the epilimnion, comprising the top warm layer; the thermocline (or metalimnion), the middle layer, whose depth may change throughout the day; and the colder hypolimnion, extending to the floor of the lake.
'lake'. [2] It is the layer that lies below the thermocline. Typically the hypolimnion is the coldest layer of a lake in summer, and the warmest layer during winter. [1] In deep, temperate lakes, the bottom-most waters of the hypolimnion are typically close to 4 °C throughout the year. The hypolimnion may be much warmer in lakes at warmer ...
The epilimnion or surface layer is the top-most layer in a thermally stratified lake. The epilimnion is the layer that is most affected by sunlight, its thermal energy heating the surface, thereby making it warmer and less dense. As a result, the epilimnion sits above the deeper metalimnion and hypolimnion, which are colder and denser.
Lake stratification is stable in summer and winter, becoming unstable in spring and fall when the surface waters cross the 4°C mark. The thermal stratification of lakes is a vertical isolation of parts of the water body from mixing caused by variation in the temperature at different depths in the lake, and is due to the density of water ...
This in turn dictates the growth and maturation of populations of organisms which tend to influence water oxygen and nutrient levels. In warm monomictic lakes, thermal stratification lends to oxygen depletion in the hypolimnion; a lack of mixing prevents the introduction of oxygen from the atmosphere into the water.
Such lakes are termed "dimictic'. During summer there is a strong thermal stratification, while there is a weaker inverse stratification in winter. (Figure modified from [2]) Mixing (overturning) typically occurs during the spring and autumn, when the lake is "isothermal" (i.e. at the same temperature from the top to the bottom).
In temperate lakes, fall-season cooling of surface water results in turnover of the water column, where the thermocline is disrupted, and the lake temperature profile becomes more uniform. In cold climates, when water cools below 4 o C (the temperature of maximum density) many lakes can experience an inverse thermal stratification in winter. [18]
A thermocline (also known as the thermal layer or the metalimnion in lakes) is a distinct layer based on temperature within a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) with a high gradient of distinct temperature differences associated with depth.