Q.What is Thermal Stratification ? Mention its three types.

Thermal stratification is the seasonal layering of a lake by temperature/density, occurring as direct (summer) or inverse (winter) stratification.

Thermal stratification is the phenomenon, seen mainly in temperate lakes, in which the water body becomes arranged into distinct horizontal layers differing in temperature and hence in density, because water density varies with temperature (water is densest at about 4 degC). A fully stratified lake commonly shows three zones:

• Epilimnion: the upper, warmer, well-mixed and less dense layer.
• Thermocline (metalimnion): the middle zone where temperature drops rapidly with depth, acting as a barrier that resists mixing between the upper and lower layers.
• Hypolimnion: the lower, colder, denser, relatively undisturbed layer.

Types of thermal stratification:

1. Direct (summer) stratification: during warm months, the surface water is heated and becomes warm and light, floating over the colder, denser water below; the epilimnion (warm) overlies the hypolimnion (cold), with a thermocline in between. …

Thermal stratification is the temperature-based layering of a lake into epilimnion, thermocline and hypolimnion zones.

Thermal stratification is the phenomenon in which a standing water body (such as a lake) becomes layered into distinct horizontal zones of differing temperature (and hence differing density) with increasing depth, especially during summer/warmer months when solar heating warms the surface water more than the deeper water, and this temperature difference prevents the layers from mixing.

The three types (zones) of thermal stratification are:

1. Epilimnion: the uppermost layer, which is warm (heated by sunlight), less dense, and well mixed by wind action; it has relatively uniform temperature throughout its depth.

2. Thermocline (metalimnion): the middle transitional layer, characterised by a rapid and steep decline in temperature with only a small increase in depth (a strong thermal gradient); it acts as a barrier that resists mixing between the warm surface water and the cold deep water.

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