Study of the Middepth Temperature Maximum in Meromictic Lakes of Kandalaksha Bay Based on Mathematical Modeling

In the coastal meromictic Lakes Kislo-Sladkoe and Trekhtzvetnoe (the White Sea, Kandalaksha Bay), the temperature regime was studied using the generalised one-dimensional model of thermodynamic, hydrodynamic, and biogeochemical processes LAKE. Particular attention was paid to the process of formation of the middepth temperature maximum (TeM). The model demonstrated the ability to realistically reproduce various physical phenomena in the annual cycle of the water body’s life, including the TeM, autumn cooling, and the winter temperature maximum. For the first time, the following factors have been assumed to have a key influence on the characteristics of the TeM and its presence: the salinity of the lake layers relative to one another, the salinity gradient exceeding 10–13 PPT/m, and the location of the salinity-gradient maximum relative to the reservoir surface. The data obtained from the modeling have been compared with field measurements.