Metalimnion
The metalimnion (metalimnial), also called thermocline , is the transitional water layer in a stratified standing water . The metalimnion forms the transition between the upper water layer, the epilimnion and the lower, the hypolimnion .
It is referred to as a thermocline because the water temperature in the metalimnion drops more than one degree Celsius per meter of water depth than in the epi- and hypolimnion. With more precise measurements, a complex fine structure was found in the metal structures of all the lakes examined. Strong temperature jumps ( thermoclines ) within a few centimeters alternate with relatively homogeneous layers. These conditions are partly the result of complex currents and internal mixing processes as a reaction to the currents and waves in the epilimnion. Mostly, however, it is a question of the legacies of epilimnion mixing events that penetrate the metalimnion to different depths, after which a warmed stratification has built up again on top.
In most of the smaller lakes, the metalimnion extends to the bottom of the lake, because the depth is not sufficient for the formation of a homogeneous hypolimnion. The layers of the metalimnion close to the ground then take on the ecological role of the hypolimnion. Such lakes are also sometimes characterized as metalimnic lakes .
The formation of layers of water occurs due to the density anomaly of the water .